Here's an explanation of some of the terms she's using: In the Harry Potter series, there are humans who are born as wizards, and there are normal humans who don't have witch/wizard/mage/whatever blood. There are several families in the HP universe that--Malfoys, for example--that pride themselves on not having a drop of normal human blood in their family lineage and believe that "normal," non-wizarding families are nothing more than primitive animals.
"Muggle" is the term for "normal" humans, the ones that aren't from a wizard bloodline.
"Muggleborns" refers to "normal" humans that practice magic and are educated in Wizard schools.
"Squibs" are people who come from wizarding blood, but don't have the ability to practice magic.