You can find very good documentation on the SQL Server syntax on MSDN: http://technet.microsoft.com/en-us/library/gg699618.aspx
In short, OFFSET 0 ROWS
means start at row 0, if you set the offset to 10 you'll get the next set of 10 rows:
SELECT * FROM VulnerabilityAlertDocument WHERE (1=1) ORDER BY Published DESC OFFSET 10 ROWS FETCH NEXT 10 ROWS ONLY;
SQL Server does not keep track of which rows you queried already, that's up to you.