This
1972 porn film was probably the most popular of all time, and was unusual at the time for having a plot. That plot is pretty thin:
Linda Lovelace's character has never had an
orgasm. Her friend tries to help her out by involving her in an orgy, but Linda still doesn't
climax. She goes to a doctor played by
Harry Reems, who discovers that her
clitoris is in the back of her throat. Performing oral sex on the well-endowed doctor finally gives her the
mind-blowing orgasm she was looking for.
She's pretty happy for a while, but then her need for a lover with a certain length becomes a challenge (because her clitoris is way back in her throat -- I think the thing she keeps saying is "I need a man with 9 inches"). I won't spoil the end for you.
I think I'd only recommend watching Deep Throat for historical interest, and maybe a couple of laughs. I saw it many many years ago, and I think seeing it now, knowing what Linda Lovelace has said about the terrible experience of making it and other pornos, it would be difficult to enjoy.