House-elves were so intensely loyal to their masters that they would not allow themselves to be set free unless their master presented them with clothes and this loyalty, in and of itself, was something akin to a code of honour among their kind…

To symbolise their enslavement, house-elves usually wore makeshift clothes made with found objects such as pillowcases and rags. These clothes could become quite filthy, and yet the elf would not clean their clothes to further express that they had no needs which were not specifically commanded to them by the master. House-elves would punish, torture, or even maim themselves if they thought it would please the master.

Despite the seemingly horrid lifestyle that house-elves endured, house-elves seemed to actually enjoy being enslaved. With few exceptions (Dobby being one of them), house-elves would feel insulted if their master attempted to pay them, give them pensions, or reward their service with anything except kindness. In 1995, when Hermione Granger began hiding clothes in Gryffindor Tower in an attempt to free the house-elves of Hogwarts, the house-elves felt rather insulted, and everyone except Dobby refused to clean the Gryffindor common room in protest.

Winky was absolutely loyal to the Crouch family, and when she was dismissed for failure to keep Crouch Jnr under control, she suffered a mental breakdown, thinking that her release was the ultimate disgrace to her family.

They were likely treated extremely well by Professor Dumbledore. In 1994, they became angry with Hermione Granger as she made attempts to free them. Dobby and Winky, who came under Hogwarts’s employ at the time, were considered disgraces to the rest of their colleagues due to Dobby being paid and receiving a vacation while Winky got drunk out of self-pity.

House-elves are freed when their master gives them a piece of clothing, this includes armour, but it seems that jewellery doesn’t count, as Kreacher was not freed when Harry gave him Regulus Black’s locket.

It may be possible for elves to breed with humans as one Ravenclaw student stated that the students in the house thought Filius Flitwick was part elf, but had never been rude enough to ask (in fact Flitwick was part goblin). Irma Dugard was also described as a half-elf.