This mystical boat helps transport Thor and other Asgardians about the universe. It provides the oxygen and gravity necessary for humans to travel along also.
The sails of the vessel are called "Proton Sails," which use "Stellar Light" to move the craft faster (Thor 1:218).
Yet as mystical as this craft is, it still is made of wood. When it is attacked, there are no 'shields' to protect it. The hull has been blasted and even had fists smashed through it.