After means ‘later than’ and ‘next in time or place’.
After can be used before a noun phrase (as a preposition):
Shall we have a swim after lunch?
The bank is just after the park, on the left.
After can introduce a clause (as a conjunction):
After I left him a message, he phoned me immediately.
She did voluntary work in a hospital after she graduated.
We use the present simple following after when referring to the future:
I’ll contact you after we reach the airport.