Patrol is a feature in the game, which lets you earn additional rewards in the background.

These rewards increase every time you progress through the worlds. You can earn up to a maximum of eight hours worth of rewards, before you have to claim them to start patrolling again.

Once you claim the rewards you have to wait up to an hour before claiming again, or if you want to, you can also use 'Quick Patrol' to gain two hours worth of rewards instantly.