It’s a true story about a girl who endured a traumatic childhood resulting in her developing 16 different personalities, each with a different name, age, and attitude. Some of her personalities were male as well!
The clips above give a good synopsis of the movie if you don’t have the time to watch the entire film.
You can find the complete film with divided parts here:
There’s an older version of the movie made in 1976 which can be found on youtube as well.
Beware, the music is somewhat creepy!