Annuity table OR Present value table

Hello friends,

Can someone advise me as to when we should look up the annuity table and when to look up the PV table.
During the APV calculation , the tax benefit was discounted by look up at the annuity table NOT the usual PV table

i am kind of confused because in the usual NPV calculation with cashflows for say 3 years we use the PV table ( the first given table ) not Annuity table

i hope i make sense. Awaiting some feedback to clarify my doubt

Cheers