Folk rhythm is a musical genre or style with roots in American folk music and rhythm and blues. It follows in the tradition of singer/songwriters like Townes Van Zandt, Johnny Cash and Jack White but sounds uniquely contemporary.
Literally, the term folk rhythm refers to the genre's roots in American culture and the oral tradition, (hence, folk) and the strum of guitar strings (rather than fingerpicking), as in rhythm guitar.
References
Folk rhythm Wikipedia(Text) CC BY-SA