Experience Points, or 'XP' are the points you gain as you progress in the game. Depending on the results of game play, you'll gain different amounts of XP:
25 XP for not completing a pattern (losing the game)
50 XP for completing the pattern (winning the game)
100 points for a full card!
Gaining XP helps you "Level up." When reaching certain Levels, you can unlock new content without spending your coins.
You can find your Level number on the top left of the game-play screen. The bar indicates XP (Experience Points) you've gained in the Level and how far you are from reaching the next Level.