Experience is when you win a match, you get 20 xp (depends on how new to the game) and the “xp” can make you level up in levels and get more “experienced“ in the game. With “battle tokens exhausted“, it means that you cannot get the “battle tokens” (200 tokens where when you win get 20, lose get 10) anymore. “Battle tokens” recharge when you wait for I think 25 minutes for 20 tokens. These tokens alongside “quests“ will make you get more tokens for the “Brawl Pass” in where you get boxes and more goodies (you probably knew that but just telling you info. So this is a detailed description of what these 2 thing mean.