MSDN – Data Access for Client Applications

Information pulled from here…

The product documentation for SharePoint 2010 includes extensive details about each of these approaches, together with examples and walkthroughs describing approaches to common client-side data access requirements. This documentation focuses on the merits and performance implications of each approach for different real-world scenarios, and it presents some guidance about how to maximize the efficiency of your data access operations in each case. Before you start, you need a broad awareness of the capabilities of each approach. The following table shows what you can do in terms of data access with the CSOM, the REST interface, and the ASP.NET Web services.