Can anyone explain to me what this code is all about?

 <?xml version="1.0" encoding="UTF-8"?>
<!--

    IIS configuration sections.

    For schema documentation, see
    %windir%\system32\inetsrv\config\schema\IIS_schema.xml.
    
    Please make a backup of this file before making any changes to it.

-->

<configuration>

    <!--

        The <configSections> section controls the registration of sections.
        Section is the basic unit of deployment, locking, searching and
        containment for configuration settings.
        
        Every section belongs to one section group.
        A section group is a container of logically-related sections.
        
        Sections cannot be nested.
        Section groups may be nested.
        
        <section
            name=""  [Required, Collection Key] [XML name of the section]
            allowDefinition="Everywhere" [MachineOnly|MachineToApplication|AppHostOnly|Everywhere] [Level where it can be set]
            overrideModeDefault="Allow"  [Allow|Deny] [Default delegation mode]
            allowLocation="true"  [true|false] [Allowed in location tags]
        />
        
        The recommended way to unlock sections is by using a location tag:
        <location path="Default Web Site" overrideMode="Allow">
            <system.webServer>
                <asp />
            </system.webServer>
        </location>

    -->
    <configSections>
        <sectionGroup name="system.applicationHost">
            <section name="applicationPools" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="configHistory" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="customMetadata" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="listenerAdapters" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="log" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="serviceAutoStartProviders" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="sites" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="webLimits" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
        </sectionGroup>

        <sectionGroup name="system.webServer">
            <section name="asp" overrideModeDefault="Deny" />
            <section name="caching" overrideModeDefault="Allow" />
            <section name="cgi" overrideModeDefault="Deny" />
            <section name="defaultDocument" overrideModeDefault="Allow" />
            <section name="directoryBrowse" overrideModeDefault="Allow" />
            <section name="fastCgi" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="globalModules" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
            <section name="handlers" overrideModeDefault="Deny" />
            <section name="httpCompression" overrideModeDefault="Allow" />
            <section name="httpErrors" overrideModeDefault="Allow" />
            <section name="httpLogging" overrideModeDefault="Deny" />
            <section name="httpProtocol" overrideModeDefault="Allow" />
            <section name="httpRedirect" overrideModeDefault="Allow" />
            <section name="httpTracing" overrideModeDefault="Deny" />
            <section name="isapiFilters" allowDefinition="MachineToApplication" overrideModeDefault="Deny" />
            <section name="modules" allowDefinition="MachineToApplication" overrideModeDefault="Deny" />
            <section name="applicationInitialization" allowDefinition="MachineToApplication" overrideModeDefault="Allow" />
            <section name="odbcLogging" overrideModeDefault="Deny" />
            <sectionGroup name="security">
                <section name="access" overrideModeDefault="Deny" />
                <section name="applicationDependencies" overrideModeDefault="Deny" />
                <sectionGroup name="authentication">
                    <section name="anonymousAuthentication" overrideModeDefault="Deny" />
                    <section name="basicAuthentication" overrideModeDefault="Deny" />
                    <section name="clientCertificateMappingAuthentication" overrideModeDefault="Deny" />
                    <section name="digestAuthentication" overrideModeDefault="Deny" />
                    <section name="iisClientCertificateMappingAuthentication" overrideModeDefault="Deny" />
                    <section name="windowsAuthentication" overrideModeDefault="Deny" />
                </sectionGroup>
                <section name="authorization" overrideModeDefault="Allow" />
                <section name="ipSecurity" overrideModeDefault="Deny" />
                <section name="dynamicIpSecurity" overrideModeDefault="Deny" />
                <section name="isapiCgiRestriction" allowDefinition="AppHostOnly" overrideModeDefault="Deny" />
                <section name="requestFiltering" overrideModeDefault="Allow" />
            </sectionGroup>
            <section name="serverRuntime" overrideModeDefault="Deny" />
            <section name="serverSideInclude" overrideModeDefault="Deny" />
            <section name="staticContent" overrideModeDefault="Allow" />
            <sectionGroup name="tracing">
                <section name="traceFailedRequests" overrideModeDefault="Allow" />
                <section name="traceProviderDefinitions" overrideModeDefault="Deny" />
            </sectionGroup>
            <section name="urlCompression" overrideModeDefault="Allow" />
            <section name="validation" overrideModeDefault="Allow" />
            <sectionGroup name="webdav">
                <section name="globalSettings" overrideModeDefault="Deny" />
                <section name="authoring" overrideModeDefault="Deny" />
                <section name="authoringRules" overrideModeDefault="Deny" />
            </sectionGroup>
            <section name="webSocket" overrideModeDefault="Deny"/>
        </sectionGroup>
        <sectionGroup name="system.ftpServer">
            <section name="log" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
            <section name="firewallSupport" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
            <section name="caching" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
            <section name="providerDefinitions" overrideModeDefault="Deny" />
            <sectionGroup name="security">
                <section name="ipSecurity" overrideModeDefault="Deny" />
                <section name="requestFiltering" overrideModeDefault="Deny" />
                <section name="authorization" overrideModeDefault="Deny" />
                <section name="authentication" overrideModeDefault="Deny" />
            </sectionGroup>
            <section name="serverRuntime" overrideModeDefault="Deny" allowDefinition="AppHostOnly" />
        </sectionGroup>
    </configSections>

    <configProtectedData>
        <providers>
            <add name="IISCngProvider" type="Microsoft.ApplicationHost.CngProtectedConfigurationProvider" description="Uses Win32 Crypto CNG to encrypt and decrypt" keyContainerName="iisCngConfigurationKey" useMachineContainer="true" />
            <add name="IISWASOnlyCngProvider" type="Microsoft.ApplicationHost.CngProtectedConfigurationProvider" description="(WAS Only) Uses Win32 Crypto CNG to encrypt and decrypt" keyContainerName="iisCngWasKey" useMachineContainer="true" />
        </providers>
    </configProtectedData>

    <system.applicationHost>

        <applicationPools />

        <!--

          The <customMetadata> section is used internally by the Admin Base Objects
          (ABO) Compatibility component. Please do not modify its content.

        -->
        <customMetadata />

        <!--

          The <listenerAdapters> section defines the protocols with which the
          Windows Process Activation Service (WAS) binds.

        -->
        <listenerAdapters />

        <log />

        <sites />

        <webLimits />

    </system.applicationHost>

    <system.webServer>

        <asp />

        <caching />

        <cgi />

        <defaultDocument />

        <directoryBrowse />

        <fastCgi />

        <!--

          The <globalModules> section defines all native-code modules.
          To enable a module, specify it in the <modules> section.

        -->
        <globalModules />

        <handlers />

        <httpCompression />

        <httpErrors />

        <httpLogging />

        <httpProtocol />

        <httpRedirect />

        <httpTracing />

        <isapiFilters />

        <modules />

        <odbcLogging />

        <security>

            <access />

            <applicationDependencies />

            <authentication>

                <anonymousAuthentication />

                <basicAuthentication />

                <clientCertificateMappingAuthentication />

                <digestAuthentication />

                <iisClientCertificateMappingAuthentication />

                <windowsAuthentication />

            </authentication>

            <authorization />

            <ipSecurity />

            <isapiCgiRestriction />

            <requestFiltering />

        </security>

        <serverRuntime />

        <serverSideInclude />

        <staticContent />

        <tracing>

            <traceFailedRequests />

            <traceProviderDefinitions />

        </tracing>

        <urlCompression />

        <validation />

    </system.webServer>

</configuration>