Well, the Manson Family situation is a major true event incorporated. Sharon Tate's real - life presence in Hollywood at that time was a real thing. The movie also reflects the types of movies being made in 1969. The real - life actors and the general feel of the Hollywood scene then are elements of the true story. Tarantino uses these real things and adds his own fictional stories of the main characters around them.
The main true event is related to the Manson Family's threat to Hollywood in 1969. Sharon Tate, a real - life actress, was a victim in the real Manson Family murders. The movie uses this as a basis. Additionally, the real - life film studios and the different genres of movies being produced in 1969 are part of the true events. Tarantino then builds his fictional narrative around these real - life aspects, showing how his characters interact with this real - world context.