What exactly constitutes "Squibdom"?

[severelysigune]

No: HPFGUIDX 88303

This is possibly a stupid question, but is there an exact definition 
of a Squib? I mean, are Squibs entirely devoid of magic (as in: the 
perfect opposite of a Muggle-born wizard), or do they possess some, 
but not enough to be a 'full' wizard/witch?

I know that: 
- Mrs Figg can at least see Dementors
and
- Filch has somehow managed to hide his "Squibdom" during his long 
career at Hogwarts (at least the students don't seem to be aware of 
it).

My questions are:

1) If Squibs have no magic at all, then the Kwikspell course is just 
swindlery. Alternatively, can magic be acquired somehow, e.g. by 
doing the Kwikspell course? 

2) And do Squibs have wands? The first lesson in the Kwikspell course 
is one on how to hold your wand, which implies you need to have one 
in the first place. If 'the wand chooses the wizard', can you just go 
into a shop and buy one, even if you are a Squib?

3) On another thread someone states that Squibs are not invited to be 
educated at Hogwarts. Is there canon evidence to support this 
statement? Also, would it not be perfectly possible for a Squib to 
study, say, Herbology, Care of Magical Creatures, Astronomy, 
Divination (at least with Trelawny), Arithmancy, Potions? 
If Squibs don't go to Hogwarts - or any other school for magic -, 
where do they get educated? Are they outcasts, banished to the Muggle 
world? That would seem very cruel indeed, especially since they 
spring forth from the magical community.

Any suggestions and answers are very, very welcome - the Squib 
business really fascinates me.

Yours severely,

Sigune