How to create Explicit enhancement points

Hi All,

I have checked many threads related to this topic. Still need some more clarification.

I know about implicit enhancement points and how to create them like in start and end places of FORM, FM, INCLUDE etc.

But what is explicit enhancement point, how to create them and what is the difference between implicit and explicit enhancement points. One difference could be implicit is SAP defined and explicit is user defined. Apart from this any other difference in the way they works or call happenings etc???