Most of you seem to insist that there is no different between a Squib and a Muggle, but that is not accurate.

If a Squib was the same as a Muggle, then Mrs. Figg would have never seen the Dementor that had attacked Harry and Dudley. She did/Dudley didn't, and she's a Squib/he's a Muggle, so, henceforth, Squib ≠ Muggle.

Originally Posted by Carole
Squibs are supposed to have a low level of magical intelligence, hence Filch could access Hogwarts and wasn't replelled by the anti-Muggle Charms.
Now, this makes sense, plus it also corresponds with what I said above. It seems that all Squibs have some latent bit of magic in them, but they simply don't have enough to actually perform magic like wizards do.