It adds a new mob to the game called a maid. At the current moment the maid doesn’t do many other things than following you around but in the future it will be able to help you with things such as gathering items, cooking and other things maids usually do in the real life.
How to “tame” a maid?
To tame (or perhaps hire would be a more suitable word) all you have to do is to give a cake to a maid. Maids wearing a white tiara in their hair are ones you have tamed (or hired).