Difference between an IS mount and a post mount disc brake

[santacruzrich]

What is the difference between an IS mount and a post mount disc brake? Is the post mount what we have been using for ages?

 

[joshbb]

yeah id love to know. just bought some new forks and brakes but my brakes havent arrived yet. im a bit unsure whether they will fit :S. there rockshox pike and juicy 3's.(IS) mount.
ps. sorry to kinda steal the thread

 

[Spotty]

Post Mount:

IS Mount:

if you do a search, this topic has been covered many a times. all your answers should be in one of those threads.