George Harrison wrote this for his girlfriend Pattie Boyd. They eventually got married.
Pattie Boyd has inspired a lot of songs. Harrison also wrote " Something" about her, and Eric Clapton wrote " Layla" and " Wonderful Tonight" for her. She and Harrison officially divorced in 1977. She and Clapton were married from 1979-1988.
The strange guitar sound is Harrison playing with a tone pedal.
Since this was the only song of his in the movie Help!, Harrison made a point of saying "I Need You by George Harrison," twice during the end credits. (thanks, Adrian - Wilmington, DE)
This is the second song written by Harrison that the band recorded. " Don't Bother Me" was the first. (thanks, Bertrand - Paris, France)