Pop Music has always been influenced by other forms of music. An important form is folk music.
Folk songs are the songs composed and sung by country people. The songs may be hundreds of years old, so nobody knows who originally composed them. Modern music is often music for dancing. In Britain it was traditionally played with instrument like flute, accordion, etc.
In the 1950s and 1960s the people who wrote songs and played them with acoustic guitars were also folk singers. The songs were often 'protest songs', complaining of bad things happening in society.