When a wrestler turns heel, they essentially become the "bad guy" in the storyline. They may start using underhanded tactics, cheating, or even attacking their former allies. The purpose of a heel turn is to create conflict, generate heat (negative reaction from the audience), and build anticipation for future matches between the wrestler and their former friends or allies.
Heel turns can be sudden and unexpected, or they can be built up over time through subtle hints and character development. Some wrestlers are naturally suited to playing heels due to their charisma and ability to evoke strong emotions from the audience.
Turning heel can be a risky move for a wrestler, as it may alienate some fans who were previously cheering for them. However, it can also be a successful strategy for building a wrestler's popularity and creating memorable storylines. Some of the most iconic wrestlers in history are remembered for their heel turns, such as Hulk Hogan's turn in the 1990s or Stone Cold Steve Austin's turn in the late 1990s.