Gilderoy Lockhart is an insufferable peacock, who is competent at precisely ONE thing: self-promotion.

And at that, he is tireless.

Actually, if you're willing to believe rumour, he is capable of some rather shady practices to convince the 'witnesses' to testify in his books as to his brilliance at all and sundry feats of fabulous sorcery. Whether it consists of bribery or the Confundus, I can't say. But it all comes to the same thing: he believes himself capable in every area and wishes everyone to listen to his ceaseless stories of how he has marvellously mastered every challenge in the great, wide world.