Position is the key thing

Whereas marginal hands from UTG are a fold, but the later the position and lack of action in front of u, the more likely those same cards suddenly become (a) playable and (b) raiseable (yeah, ok, that isn't a proper word!)

e.g AJ off from UTG is more than likely a fold, whereas AJ off from middle-to-late position suddenly has raising potential. Same with small pp's from same position. UTG I am more likely to chuck them, whereas middle-to-late, I am more free to limp and, in the right situation (but less often maybe) raise.