Frame trap is pretty much defined in it's name.. its a situation in which you do a move that leaves you with frame advantage on block, followed by another move that comes out fast enough to take advantage of the last move's static difference.. in order to leave the other player with limited options.
IE. player 1 does a move that leaves him +3 on block, followed by a move that comes out in 5 frames - there are only 2 frames in between where player 2 is free of block stun, without a move that goes active in those 2 frames, player 2's options limited to block, 1F jump, backdash.
Working off frame traps is how you create good mix ups, for example if player 1 has a move to beat out back dashes he creates a mixup where he can do that first move, and a)follow thru with the frame trap and continue pressure b)tick throw c)hit your back dash for a combo d) attempt an anti air for your jump.
As far as a gimmicks/shenanigans go.. it's more like tricking them to continue pressure / or create a mix up.. something that is escapable on a technical level.. but mentally, they fall for the trick and you profit.. Gimmicks aren't all bad, but not solid enough to depend on. You need to first establish your technical ability to your opponent, before you make use of gimmicks.