House-elves are small creatures which serve a wizard family for life. They do chores such as cooking and cleaning for them. They generally do not get paid. They can only be set free- often against their will- by being presented with clothes. The first house-elf to appear in the story is Dobby, who serves the Malfoy family.
House-elves are magical creatures with bald heads and large, bat-like ears. House-elves serve wizardkind, and many of the oldest, richest wizarding families have a house-elf bound in their service. House-elves must obey their masters absolutely, and some will physically punish themselves for what they consider failure or disobedience.
A house-elf can only be freed if its master presents it with an item of clothing. Because of this, and as a mark of their servitude, they fashion clothing out of other pieces of material, for example tea-towels and pillowcases.
Hogwarts has the largest number of house-elves of any dwelling in Britain, according to Nearly Headless Nick, at over a hundred. The house-elves restrict themselves to the kitchen for the majority of their day, leaving at night to do a bit of cleaning, amongst other chores. According to Nick, the mark of a good house-elf is that you don't know it is there. Nick maintains that house-elves don't want sick leave or pensions, and are happy to work in the conditions they do.
The practice of house-elves being attached to wizarding families goes back centuries. Currently elves are under-represented within the Department for the Regulation and Control of Magical Creatures, a fact Hermione wishes to change.
The house-elves who work in the Hogwarts kitchens all wear the same uniform; a tea-towel stamped with the Hogwarts crest tied like a toga.
The house-elves are delighted when Ron praises their quick service, after providing tea within seconds of it being requested. As Ron, Harry and Hermione prepare to leave the kitchens later, many of the surrounding elves press in upon them, offering snacks to take back upstairs.
Dobby tells Harry that house-elves are not allowed to speak their minds about their masters, as a part of their enslavement. A free-elf is able to speak about their old masters' however they please, although even those such as Dobby, who are happy to be freed, struggle with this concept.
The house-elves in the Hogwarts kitchens appear worried that Harry, Hermione and Ron will judge them all by Winky's behaviour. They are not concerned that Winky is desperately unhappy, as they feel she has no right to be unhappy when there is work to be done and masters to be served. The cheery smiles vanish from their faces when Hermione tells them they have a right to wages and holidays, and that they don't have to do everything they are told. They see Hermione's beliefs as dangerous, and look at her as though she is mad. They usher the trio swiftly out of the kitchens after Hermione's outburst.