Step-by-step explanation:
Issen Sengeki... Messatsu!
In FNaF, we have the player as the night guard, and simply- our goal is to watch over the Animatronics. We'd all like to think that, but there's a little more depth to the actual story itself. In the first FNaF, a newspaper highlighted as "Help Wanted!" Is shown, stating that the Pizzeria needs a new lifeguard. As we take our first night in, a phone rings. Phone guy is somewhat of a mystery himself, but he gives us a little background to what's happening. He tells us that the Animatronics "Magically" moves throughout the night, and we have to keep an eye on them.
In the sequel, FNaF 2, the old place is closed due to the Animatronics "Malfunctioning". Few years later, the Pizzeria has a grand re-opening. Much like the old Animatronics, we have these "Toy" Animatronics. The old Animatronics are put in the basement room to be forgotten. We have two newcomers, Mangle and Puppet. Mangle is an Animatronic, in contrast to Puppet/Marionette.
You shouldn't take this information just from me. Search up different types of information like Wikis for different opinions.