A tech card is something that you add in. It is not your main focus of the deck, but it often helps against other decks. For example, if my deck has problems beating Donphan, I would use a tech card to help beat Donphan.
A Snipe card is something that attacks the bench. These guys often do a small amount of damage to a single pokemon on the bench, and fail to be affected by weakness and resistance.
Any other vocab you should know? A donk is when a game has been won on the first 2 turns of play. That's about all I can think of.