You have given very little detail to give any answer.
SharePoint is based on ASP.NET so you could do data access the same as you would in an ASP.NET application. However, SharePoint also has built-in functionality, such
Business Data Catalog[
^] in 2007 that is used to expose external data.
Before jumping straight into SharePoint it would behoove you, and your company, to spend some time actually learning what it is and how to use it.