Updated Wed, Jan 16, 2013 by gunky
One of the aspects that has appealed the most to me throughout the Elder Scrolls franchise has been the wide-open character class system. Or, rather, the persistent lack of one. The skill-based character allows for much more freedom and customization - you can totally tailor your character to how you want to play the game, rather than be forced along a progression track by a rigidly-defined class.
Most MMOs use very narrow classes with a tree of trainable skills that make that character really good at one job. With the Elder Scrolls games, your character was defined by his actions; if he chose to wear full plate armor while sneaking around stealing things and killing enemies with magic, he got better at all of those things. Picking a "class" at the start of the game was optional. You could invent your own class with the collection of skills and powers you wanted to use.
TESO will be somewhat more restrictive than previous Elder Scrolls games. It will use set classes that come with unique skill sets, like special attacks, magic and other powers, and will level up by gaining experience rather than by skill-usage. But these classes will not be gear-restricted. There's no reason your character can't swing a tiny dagger while wearing full plate armor, or pair a mighty two-hander battleaxe with fire spells. Whether you'd actually want to do these things is debatable, but that decision is yours to make. Your class is a jumping-off point rather than a career commitment.