Depends if you are going off the Norse mythos or the Marvel Comics(movie & Comics).

In the myth he was given the hammer at birth but was sabotaged to prevent him from wielding the power destined to him to prevent Ragnarok. But once given to him the hammer could shrink so it could be carried, and thrown it would always return to him(easier because of its compact handle now), And summon Thunder/lightning to strike his foes.

All Asgardians were supposed to be of higher physical ability than humans. Stronger, Faster, More durable, healing. Usually their weapons/equipment granted them extra abilities such as the hammers lightning. Sifs winged horse of flight. Heimdals Helm of vision.

Marvel comics makes a few alterations but because it is so prominent it should be pointed out. Thors hammer was sabotaged by Loki in marvel. All asgardians have extremely high strength, speed, reflexes, durability with most abilities actually part of the person, not equipment. Thor loses most of his abilities and powers if separated from the hammer for too long. For a while he shared a body with a mortal, if his powers faded enough he reverted back to his mortal human form but no longer.