Trophies are won or lost after each Arena battle. You gain Trophies by defeating other players and lose them if you're defeated.

The more Trophies you accumulate, the higher you will place in the PvP Arenas. If you lose Trophies, you may also be demoted to lower Arenas.

If other players battle you while you're away, a pop-up will let you know how many Trophies you have won or lost the next time you enter the PvP Arenas.

You can see how many Trophies you have by checking the Trophy icon on the left of the main screen or by entering the PvP Arenas.