What does NP complete mean?

A proof of P = NP could have stunning practical consequences, if the proof leads to efficient methods for solving some of the important problems in NP. Many NP-complete problems are fundamental in many fields. One negative impact is that many forms of cryptography, notably public-key cryptography, would become trivially easy to "crack" and would therefore be useless. However, there are also enormous positive consequences that would follow from rendering tractable many currently mathematically intractable problems. For instance, many problems in operations research are NP-complete, such as some types of integer programming, and the travelling salesman problem, to name two of the most famous examples. Efficient solutions to these problems would have enormous implications for logistics. But it is by no means the only field that would be profoundly changed. To take one of very many examples, important problems in Protein structure prediction are NP-complete ; if these problems were solvable efficiently it could spur considerable advances in biology.