Types of Skills

There are some nice in-depth articles on this site, but I can't seem to locate some much information on the very basics of the game. One question in particlar:

What are all the different types of skills, and what differentiates them (other than the name)? I've seen descriptions of:

attack
stance
spell
enchantment (is this a subtype of spell??)
signet
glyph

Attack Skills
-Pet Attacks
Spells
-Hexes
-Enchantments
Stances
Shouts
Glyphs
Signets
Nature Rituals
Preparations
Skill