Well mine hasn't started yet so I can only speak about what I read.

A volunteer homestay is an agreement whereby a guest stays with a host in exchange for work. The guest gets a place to sleep, usually they eat with the host and they sometimes get some small pocket money. In exchange, the guest works for 3-5 hours a day helping the host out with whatever they need. This can be cleaning the house, cooking, gardening, farming, taking care of the animals, babysitting or petsitting. It all depends on what they agree to beforehand.

This is most popular among tourists who want a cheap stay on their vacation, but there are other reasons too including language learning.

You find homestays on platforms like Workaway, Worldpackers, or WWOOF(organic farm stays only). They are paid platforms.

From what I've read online in past experiences, it's hit and miss and depends a lot on the host. Some people say they had an amazing experience, it changed their life, they made lifelong friends, and learned a lot about the work and learned the language. Others had a very bad experience, their host didn't provide necessities and expected them to work more than 5 hours etc. I recommend you contact past guests of a particular host, even if their review is positive they will be more candid in private and you can ask specific questions.

Remember you can leave whenever you want. There is no signed contract or obligation. And you should not let yourself be taken advantage of. If a stay is bad, leave early. Worst thing that can happen is you get a bad review.