好き is an adjective in Japanese but in English it would be a verb. Why does does it become an adjective instead of a verb?
Japanese grammar reflects their way of thinking. In English "to like" is an action that you do to a thing, but in Japanese "be liked" is a quality that a thing has. If you think it like that it's easier. The subject particle is が, so the thing that you like must be marked with it. The person who likes it must take the particle of topic, は. For example, 私はりんごが好きです means I like apples (or apples are liked things for me).
好き can be used as a verb, like パンが好き (I like bread,) as well as an adjective 好きな人. Or for that matter, as a noun, 男好き.
"Why does it become an adjective instead of a verb" is a strange question to me, because it implies you think it shouldn't be an adjective, but I find it quite natural that it takes that form, like "favorite."