Jean-Luc Picard is Captain of the USS Enterprise, which hails from the Trek Galaxy. The Humans there have an organisation set up there to defend them, known as the Galactic Federation. Picard rose up the ranks of the Federation because of his awesomeness, and ended up captaining one of their best ships.
He went on many adventures and fought many alien races, like the Romulans, Klingons and Borg. However, and possibly more importantly, he also secured peace between the Federation and a lot of alien races. He was the Captain who secured the cross-galactic alliance between the League and the Federation.
He is deeply respected by his crew, especially by his First Officer, Commander Riker. He is good friends with Data and Beverly Crusher as well as the ship's Counsellor, Deanna Troi.