Basically you have your first spec..

When you learn a second spec, the bars appear the same (ie buttons in the same places), but its actually a second set of bars.

The talents are new, you can glyph the new talents however you like. You edit the bars, for example putting heal spells on, instead of dps stuff, etc..

When you switch back to your first spec, you have the talents, original glyphs and original bars. The next time you switch to the 2nd spec, the changes to the bars remain etc.

You still have only one set of macro's within warcraft. A total of 18 for the character specifically, and however many (I believe 90) that are shared between all toons on the account.