CAML stands for Collaborative Application Markup Language. CAML is an XML based language which provides data constructs that build up the Sharepoint fields, view, and is used for table definition during site provisioning. CAML is responsible for rending data and the resulting HTML that is output to the user in Sharepoint. CAML can be used for a variety of circumstances, overall is used to query, build and customize Sharepoint based sites. A general use would be building a CAML query in a Sharepoint WebPart in order to retrieve values from a Sharepoint list.