Remember how 庶民 means "common people"? Well, anything that's "common-people-like" is ordinary, unpretentious, and approachable.

Unlike 庶民, which can sometimes have negative connotations, 庶民的 is usually positive. It's used for things that appeal to ordinary people, like an unpretentious restaurant or a person with a familiar, approachable vibe.

This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.