Within the slasher genre, there are several common conventions:
1) A masked killer goes on a killing spree of a group of teenage friends who engage in rule-breaking behavior like sex and drugs.
2) One by one the teenagers are killed until only the "final girl" remains to confront the killer at the end.
3) Common slasher elements include the killer's masked identity and signature weapon, scenes of victims suffering graphic deaths, and a "final girl" who survives through intelligence and bravery unlike her peers.