House-elves are small humanoid creatures who inhabit large houses belonging to wealthy Wizarding families. They are "bound" to the family of the house, which means they do all manner of menial tasks for them until they die. House-elves are apparently very happy with this arrangement and consider it a matter of pride that they serve faithfully and do not betray their families.
Don't worry: he'll only be released from his enslavement if Lord Volder-Jensen gives him new clothes. Since I'm not his master he's happy to wear anything I send him.