A Wicket in Cricket means two things.
The Wooden sticks behind the batter....
...and the ENTIRE pitch a game of cricket is played on.
To use your bat to hit the ball and score as MANY runs as possible within a set amount of tries (also called balls) from the opposition to get you out.
After hitting the ball a batsman can run in-between the wickets (the wooden sticks on either side) and everytime they run between them they score a run!
The goal is to get the batsman out by catching the ball after he/she hits or EVEN hitting his wickets with your ball. You can even run the batsman out which simply means you hit the wickets with the ball when they're running between the wickets to make a run and they don't get to the wicket fast enough.
To stop the batters making runs and get the ball back to the middle as soon as possible before the ball goes ALL the way to the edge of the pitch (the boundary) where the batter makes extra runs if it does (a 4 and a six if it goes over without bouncing)!
A fielder can also catch the batter out if they catch the ball before it hits the floor after being hit by the batter.