You can buy Snapchat Score from the app store. It is a service that lets you track your snaps sent and received. You will see a point for each snap you send in the corner of the screen when you send a snap.
When you receive a snap, your Score will go up as well. If you open a new snap, your Score will increase even more. Snapchat updates your Score every time you open an unread snap. Your Score is a measure of how popular you are on Snapchat. People send and receive snaps from you often if you have a high score. Snapchat support can help you if you have any questions about your Score.