What's the difference between integrated and ahead forks?

billa looking to get carbon forks my bike has standard ahead and a lot of forks i've seen are advertised as integrated headset only, i cant see what would make them incompatible with aheadsets???

My only guess would be something to do with where/how the crown race sits on the top of the crown ?

Flat top on the top of the crown = integrated / more curved round top of the crown = standard headset.

Just a guess though. ????