What is cribbage? How do you play it?
Cribbage is a card/board game. It is played in rounds, fifteen is part of the main scoring along with same kinds, runs and flushes. 
Is it a standared 52 card pack game?
Yes, and score is kept by moving pegs around as board until someone gets to 121 and wins.
Is that a long game? I feel like it would be if you have to get all the way up to 121. 
A typical game is 10 or 11 rounds and each takes only a few minutes, so 20 to 40 minutes a game.
Thats not too bad! That is about the average time for any game. I guess I just thought it would be longer. Do you play with a group of people very often?
It is best played wit 2 players  and I only know 2 people who play it. 
How do you score?
Fifteens are 2, runs and flushes one per card, matches 2 per 2 matched and 2 for some a Jacks.