You can see exactly how it's played in the picture, the numbers are referring to the amount of mines they are in contact with, and off that you just try to evade all of the mines and click on all of the spaces.

Join the club, brother.

www.youtube.com/watch?v=LHY8NKj3RKs

Disregard all of that, just watch this.
It's the proper way to play.

It's pretty easy actually. You click on a square. The number that appears is how many mines are next to that square. It refers to the directions above, below, to the left and right, and the 4 diagonals inbetween those. Just the adjacent square, however. Then you continue like that, using logic with the numbers to right click and flag all of the mines that are hidden and left click to uncover the safe spaces.