OP is a calling station, who tries to make moves sometimes.
A hand earlier: I raise UTG AQo, 2 callers, flop was 665, checked around, turn Q, I bet he calls, river A I bet he calls, he had 67s.

Effective stacks 200.

Preflop: UTG (villian) limps, SB, completes I check on the BB with .
Flop (6) : ,
SB bets 3 I raise 10, UTG calls, SB folds
Turn (26):
I bet 20, UTG raises to 45.
I?

Do I try to keep pot small by calling turn, check/calling river? He is going to bet about 1/3 of the pot IMO.
Or do I play for it all?

IMO, I play for it all with a flush with shallow stacks.

3bet means make the third bet (of whatever amount). 4bet would be the next (and USUALLY final raise, since it's usually an all in in NL if it gets to a 4bet). Heck, 3bets are usually all ins.

It's more common in limit, but it's just a general term for which bet has been made, the first open bet, the first raise (2bet), the 2nd raise (3bet), etc...

ps some stupid house rules have that you can only make a bet and 3 raises EVEN IN NL (at least one of the poker clubs here has it...it's absurd).