Someone who's parental acts the way a typical mother or father does. A parental kindergarten teacher might pat students' heads and call them "sweetheart."
You can use the adjective parental to describe a motherly or fatherly person, like your parental uncle who attends all your school plays. It also describes something generally related to parents — like parental leave, a work benefit that allows new parents to take some time off to care for their baby; or a parental advisory, which warns parents about the content of an audio recording. The Latin root of parental is parens, "father or mother."