The API is, effectively, a contract that the Sharepoint team has exposed. What this means is, if you supply a web request to the appropriate API "endpoint", some action will be taken that corresponds to the call you have made; this might be to update something, retrieve data, and so on. Now, these APIs are exposed as REST APIs, which means that any code that you write is going to have to be able to communicate over HTTP following REST conventions.
To be honest, doing this in VS2005, while possible, is going to require you to write a lot more code than if you were using a later version of VS and ASP. Is there a reason you have to stick with this platform? If you absolutely must use VS2005, then you need to follow the instructions and link from
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