People often wonder what a rhythm guitarist does in a band. What is his or her role? Well, there is actually no rule that differentiates a rhythm and lead guitarist. Both roles can be reversed. For example, the lead guitar may do some strumming while rhythm will do some picking. As long as what they do complement each other then there is no conflict.
However, the rhythm guitarist must be part of the rhythmic structure of the song being played. The sounds that come from the rhythm guitarist should add body to the music being played. To be more graphic about the two roles. We can take a sheet music or tablature of a song with chords marked and plays the song through using just one guitar playing the chords marked on the music. This is the rhythm guitar part. If there is any other guitar sound in the song then that is the lead guitar.
A good technique to learning rhythm guitar is by listening to band music and zooming into the rhythm part. Bands like The Shadows, The Who, The Beatles and The Moody Blues have defined rhythm guitars and they can be good reference.
Another way to study rhythm is to listen to the drummers and bass players. Try to feel the rhythm of a song and see if you can play along using chord strumming. The goal here is to fill a necessary role in the music’s rhythm.
Practice with a low volume first and experiment with your guitar strumming. You could try muting strings and not strum using the 6 strings, leave some of the music to the lead and bass player to fill up.
The lead guitarist plays for solo breaks or extended solos during a song and may not follow the basic rhythm of the song. The body of the song rests upon the rhythm guitarist.