I hadn't thought, chilled is quite a subjective term come ot think of it. The best word that I can come up with to define it for me would be mellow, it has to be light for me. Downtempo/IDM type music and classical music can both can fit under the term chilled for me. There are many genres which have songs which I'd refer to as chilled from acoustic to ambient to even some liquid dnb, it really depends on the song. Genres which I wouldn't consider to be relaxing whatsoever would be metal and all the subgenres and genres related to that.
Sorry I didn't think about it before but it's a very vague and subjective question. But I hope what I've said narrows it down slightly.