SQL server stores the temporary data in INSERTED and DELETED table while working on triggers.
I give u an Example...
If u have just inserted a row in the table T1, u wont be able to get this row from T1 within the Trigger. You can retrieve this row from INSERTED table.
SQL Server uses INSERTED Table for INSERT and UPDATE trigger, DELETED is used by DELETE Triggers.
There is no UPDATED table as some people get confused.