A category of computational problems based on their complexity as outlined briefly below.
P (Polynomial Time)
Problems can be quickly solved. See
polynomial time.
NP (Non-deterministic Polynomial Time)
Problems can be quicky verified.
Co-NP (Complement of NP)
If NP is yes, Co-NP is no.
NP-Complete
Difficult problems.
NP-Hard
Hardest problems to solve.