Five Nights At Freddy's is a game about how you play as a security guard working the night shift in a pizzeria. They have robotic animals that play with the kids during the day but roam around at night. If they see you, you lose.
You must look through a series of security cameras to spot the animal's location. If thy are close to you, you must shut the corresponding door. If you are unsure, you may shine a light down the hallway.
Shutting doors, shining lights, and viewing cameras all take energy. When you run out of energy, you also lose.
The goal in the game is to survive five shifts, one increasingly harder than the last.