The word "Au Pair" is a French term, which means "on par" or "equal to", denoting living on an equal basis in a reciprocal, caring relationship between the host family and the children. An aupair will typically be a young woman and sometimes a young man from a foreign country who chooses to help look after the children of a host family and provide light housekeeping. The aupair is given room and board and is typically paid a weekly "pocket-money" salary. Aupairs generally stay with their host family for one year.
I spent a year in England as an au pair.