From the BOL:

Is used to indicate the sequence of SQL Server activity on a row, represented as an increasing number in a binary format. As a row is modified in a table, the timestamp is updated with the current database timestamp value obtained from the @@DBTS function. timestamp data is not related to the date and time of an insert or change to data. To automatically record times that data modifications take place in a table, use either a datetime or smalldatetime data type to record the events and triggers.

>Hmmm... so, what if you inserted a record into the table and read the timestamp save it. Two days later, come back and update that record, read the timestamp... Then, all the records where timestamp between timestamp1 and timestamp2 would be the records that were already updated???

Yes

-Mike