Many people choose to learn to play guitar when they are still at school. If you want to be in a band you might want to learn to play guitar or the drums or the keyboard. Many people learn to play more than one instrument. Once you can play one instrument, learning others is generally easier. Learning how to read music is especially useful.
A private guitar teacher can help you learn to play guitar quickly. Different styles of guitar playing require different skills - learning to play Spanish guitar for example will require far more time and effort than playing some rock power chords!
People do have a certain natural ability when it comes to playing music. You may become frustrated that your friend manages to learn to play guitar far faster than you do.