It differs from the term Squib, which refers to a person with one or more magical parents yet without any magical power or ability, and from the term Muggle-born (or the derogatory and offensive term mudblood, which is used to imply the supposed impurity of Muggle blood), which refers to a person with magical abilities but with non-magical parents.
The most prominent Muggle-born in the Harry Potter series is Hermione Granger, who was born to Muggles of undisclosed names.
In the Harry Potter novels, Muggles are often portrayed as foolish, sometimes befuddled characters, who are completely oblivious to the wizarding world that exists in their midst.
These include Muggle parents of magical children, such as Hermione Granger's parents, the Muggle Prime Minister (and predecessors), the Dursley family (Harry Potter's unsupportive non-magical and only living relatives), and the non-magical spouses of some witches and wizards.
Rowling has created the word "Muggle" from "mug", an English term for someone who is easily fooled.