Usually members of the teaching staff, this term means more in some schools than in others.
In day schools, it will depend on how seriously the school takes the house system and may not be all that important.
In boarding schools, it is almost always a prestigious position; the housemaster or housemistress acts on behalf of the child’s parents while they are at the school. Make sure you trust the one in your child’s house and that he/she will get on well with your child. This is usually the first person you should contact if you are worried about your child’s happiness or health. While the Head has a massive influence on the school overall, the individual houses can vary according to the personality of the housemaster/mistress in charge.