J.K. Rowling called people without magical ability “Muggles” in the Harry Potter series. The term generally refers to non-magical people who are not born into the wizarding world.
Muggles can be unaware that witches and wizards exist, although some characters know about magic through family or personal contact. Hermione Granger, for example, is born to Muggle parents despite being a witch, while Harry’s aunt and uncle are Muggles.
The term is distinct from “Squib,” which describes a person born into a wizarding family who cannot perform magic. It is also different from “No-Maj,” the term used for non-magical people in the American wizarding community shown in Fantastic Beasts. These vocabulary differences are a frequent source of confusion among readers.