Battle points are Tank Fighter's trophy system. The more you have...the more badass you are. Edit
When you win matches, you receive battle points. The more hit points you have when you destroy your enemy, the more battlepoints you receive. On the same token, when you lose matches, you lose battle points. The fewer hit points your opponent has, the fewer the battle points that are subtracted from you.
When you dominate an opponent with more battle points, you get more battle points for your win. If you get dominated by an opponent with more battle points than you, you'll lose less.
Why have battle points in the first place? Battle points influence matching. When you rev up your tank engines and prepare to roll out on to the field for your next fight, you are being matched with someone with a similar number of battlepoints. You're playing an opponent worthy of a fight, either based on their skill alone, or their advanced, mean machinery. Regardless, battlepoints make sure that each fight is worthwhile.
Battlepoints also make sure that you receive all the glory you deserve with local, and global rankings. So work your way up Tankfighters! Get back in the arena!