The goal is to clear the board. This is done by tapping a square to reveal what is behind it. The numbers on the board show how many mines are present in the 3x3 area around the number.
Swipe a square to indicate you believe a mine is behind that sqaure. This helps you to play effectively and prevents you from tapping that square.
There are many versions of Minesweeper and many common tactics. Look online for more information on effective play.