A maid is a household worker who cleans and performs various other tasks. Today, only very wealthy people have maids — it's much more common to hire an occasional housekeeper or cleaner instead.
In the US, it's uncommon to find a household with an actual maid, a servant who lives in the home and tidies it up, also doing jobs like ironing, grocery shopping, and cooking. In the old days, wealthy families employed maids who wore uniforms and sometimes waited on one individual woman, helping her dress herself and cleaning up after her. Maid, short for maiden, originally meant "unmarried woman."