Maybe you're a new football fan who is hoping not to be too confused while watching a Euro 2016 football game.
Maybe you're not a football fan but you don't want to sound silly in front of your family and friends who are football fanatics.
Whatever the reason may be, watch this video quickly to be clear about Uefa's Euro 2016 Championship rules.
What is new this year would be the introduction of the goal line technology.
For the first time in Euro history, this technology will be used to rule out uncertainty of whether the ball had crossed the line.
This system will help to ensure that goals are counted in a fair manner, and hopefully reduce the number of "referee kayu" situations.
Watch our video for this, and a few more crucial rules quickly explained.