A Tick Throw is a specific technique where a player does an attack with little blockstun (like a 2A or 5P), and immediately throwing the opponent afterwards.
This takes advantage of the fact that fast attacks with little blockstun usually have frame advantage. The opponent expects a Frame Trap and decides to block instead of attacking back or jumping out.
A few tick throw examples
Throw Protection
Almost all fighting games have a bit of throw protection after blockstun. This means that the opponent is invincible to throws even after exiting blockstun for a few frames (the exact amount varies from game to game). If your tick throw whiffs even though the opponent is clearly in range, then try delaying your throw slightly.