You don't specify what version of DP so, I will assume DP 8
In your GUI, click on Help ->Guides and pick the integration guide for Microsoft Applications. There are similiar Guides for DP 7 and 9. This Guide may also be downloaded from
Section II discusses backing up the Microsoft SharePoint server.Table 19 describes the various type of backups
Full
====
Microsoft SQL Server database:
Performs a Microsoft SQL Server Full database backup;
the complete database is backed up.
Index files:
Performs a Full filesystem backup of all index files.
Incremental
========
Microsoft SQL Server database:
Performs a Microsoft SQL Server transaction log backup.
Backs up transaction logs (.log) that have been created since the last transaction log
backup of the Microsoft SQL Server database, and then truncates the transaction logs.
Index files:
Backs up only the index files that have been changed or created since the
last backup of any type.
NOTE:
If the Microsoft SQL Server database is in the simple recovery mode (has no transaction
logs), a Differential backup will be performed for the database instead.
For the metadata of the Microsoft SharePoint Server 2007/2010 components, a Full
backup is always performed due to a small amount of data.
Differential
========
Microsoft SQL Server database:
Performs a Microsoft SQL Server Differential backup of
the database; backs up changes made to the database since the last Full backup.
Index files:
Backs up the index files that have been changed since the last Full backup