Slasher movies typically feature certain tropes:
1) The final girl who survives is often darker haired and less sexually active, meant to convey that sex is dangerous.
2) The monster wears a mask, making it scary because it could be anyone underneath and adding to the creepiness.
3) A group of friends who are without parental supervision are usually targeted when the monster attacks.
4) These movies often feature a benefactor, usually an older character like a police officer or doctor, who is seemingly committed the killings but is ultimately revealed to not be at the end.