Your job consists of keeping an eye on Freddy and his friends during the night through the security cameras. That said, because of a budgeting problem, you'll have a limited amount of electricity that you can use each night, and if you run out, well, you'll be at the mercy of Freddy and his friends, which in the second part are more numerous and aggressive than ever.
The controls in Five Nights at Freddy's 2 are very simple: at any moment you can close the room's security doors to protect yourself, although this consumes a lot of electricity. You can also switch security cameras, which consumes a bit less energy.
Five Nights at Freddy's 2 is a horror game that despite its rather abnormal premise manages to give more than one good fright. In the free trial, you'll only be able to play the first night, but that should be more than enough to get a taste of the terror and shocks awaiting you in the full game.