According to Wikipedia, The Free Encyclopedia, "a nanny is a person who looks after the child or children of one family in their — the child's — home. Modern nannies may live in or out, like other domestic workers, depending on their circumstances and those of their employers.
The same source a Wikipedia, The Free Encyclopedia, defines au pair as "an Anglicization of the French term "au pair," which means "on par" or "equal to" and describes a young person living on an equal basis with a host family in a foreign country. The au pair helps the family with childcare, housework, or both while staying as a guest of the family and generally receiving a small allowance (or pocket money). An au pair will typically be a young woman, or sometimes a young man, who is accepted into the host family as an extended family member. Both the family and au pair are expected to respect cultural differences and display tolerance towards one another.
An au pair placement is an arrangement where an unmarried person between 17 and 30 years old lives for up to two years in a foreign country as a member of a local family, helping in the home for a set number of hours a day, often with at least two full days off per week. In return, they receive a reasonable allowance and a private room.
An au pair shall be treated as an equal part of the family, not as a servant, and shall not be required to wear a uniform. There can be misunderstandings on both sides about what this means. The usual practice is that Au pairs eat with the family most of the time, and join in some of the usual family activities such as outings and trips. However, host families normally expect to have some private time to themselves, particularly in the evenings. During this time, an Au pair might retire to his or her room to watch TV or study, or go out with friends. Being an Au pair can be a great opportunity to experience a different country and culture. The "job" of the Au pair will vary depending on how much the host family expects, although there are government set limits as to how much you are allowed to work. Jobs vary from taking/picking up kids from school, taking the kids to after school classes, cooking, cleaning, ironing, babysitting,etc. The au-pair is given a monthly allowance and all living/insurance/food expenses are paid by the host family.