difference between np complete and np hard

greetings!!!

could anybody tell me the difference between np hard and np complete (in simple way). I have read articles on many sites but they are a bit complex.

now this is what I think

np complete problems are those problems whose solution can be verified in polynomial time by a non deterministic turing machine.

np hard problems are the hardest problems whose solution might not be verifiable.

please do correct me if i am wrong.

also a problem is np hard if there exist np complete problem that is reducible to np harp problem

thanks