Learn Russian: Зимой я отдыхаю дома.

In Russian, to say when something happens during a season, you generally do not use a preposition. Instead, you change the ending of the season's name. The base noun зима (winter) changes to зимой (in winter). This uses a grammatical form called the instrumental case.

Why does "at home" use the word дома instead of a prepositional phrase like в доме?

The word дома is a fixed adverb that specifically means "at home". If you used the phrase в доме, it would literally mean "inside the house" (referring to the physical building) rather than the general concept of being at home.

I learned earlier that дома means "houses" (plural). Is it the exact same word?

They are spelled identically but pronounced differently! The adverb for "at home" has the stress on the first syllable (дОма). The plural noun "houses" has the stress on the last syllable (домА).

Does the verb отдыхать (here conjugated as отдыхаю) mean anything else besides "to rest"?

Yes! While отдыхать means "to rest" or "to relax", it is also the most common way to say "to vacation" or "to be on holiday" in Russian.

Since our current lesson is about expressing likes, how would I change this sentence to say "I like resting at home in winter"?