That is a very basic question. I suggest you do a search on it before posting (or migrating) this question to CrossValidated.
– SotosJun 24 '16 at 11:47
see http://stats.stackexchange.com/questions/112451/maximum-likelihood-estimation-mle-in-layman-terms/171468#171468
– Jun 24 '16 at 13:51