P stands for polynomial , NP stands for Non Deterministic polynomial
P⊆NP // Every P is NP , but not every NP is P
P problems can be solve in polynomial time by a deterministic TM.....
NP problems can be solve by any DTM in exponential time , but by NDTM in polynomial time..
P problems are those that we can solve as well as verify in polynomial time
NP problems are those , for which a polynomial time solution is not necessary but if somehow we have solution , we can verify that solution in polynomial time...i mean to say for correct input we can verify NP problem in polynomial time....it's not close under complement means for incorrect , we can't say we can verify in polynomial time....
hardest problems in NP are called NPC ...they are intractable because they have no known polynomial time solution ...
P is closed under complement ....P problems are trackable problems (problems that can be solve in polynomial time)
P , NP , NPC all are decidable problems , NPH may or may not....
web is full of contents about P,NP , just google
