CNF vs Horn Satisfiability -

I know it's easy to prove whether a horn-formula is satisfactory. My question is: Why is it easy with the horn formula instead of the usual CNF?

Appearance or absence can be shown in linear time. A good start with some examples can be found without back tracking.

A Berode University pseudocode

There is a classic problem satisfying for general CNF expression. A polynomial time algorithm is known for the satisfaction of CNF (except if P = NP ).