[nyrikki]

Thinking of this way helps me.

NP-complete is the intersection of sets NP and NP-hard , but not the part of NP that contains P.

Lots of NP-hard problems are not in NP is important.

[gbacon]

See this helpful diagram:

https://en.wikipedia.org/wiki/NP-hardness#/media/File:P_np_n...