In combat, you have three defensive options.
Standard Action defense options:
* Total Defense - standard action, gives +4 dodge bonus to AC. Can't use with Combat Expertise however. Can't make AOO while fighting defensively.
* Fighting Defensively - standard action, +2 AC but -4 To Hit, can be used with Combat Expertise
Full Round Action defense option (as when making multiple attacks)
* Fighting Defensively - Full Round Action, +2 AC but -4 To Hit
While this isn't really new, it is remarkably more clearly presented.