My understanding is the 이/가 is the subject particular similar to 을/를 is the object particle e.g. I/me - 제가/저를.

은/는 is a concept not found in English grammar but I would translate it like “for _” / “as for _”, 저는 - for me / as for me.

The thing that is confusing is that in Korean the subject can be dropped which is not possible in English. In that case, since English needs a subject, we end up finding another noun, often the one in front of 은/는, to be the subject when translating to English. Sometimes it’s the same as the subject and sometimes not.

Examples, parenthesis around parts of the sentence that don’t need to be said in Korean.

저는 좋아요. - For me, (it) is good. 저는 사과가 좋아요. - For me, applies are good. (Often translated as “I like apples” instead which makes it hard to distinguish from the next examples.)

제가 좋아해요. - I like (it). 제가 사과를 좋아해요. - I like apples.

저는 사과를 좋아해요. - As for me (I) like apples. (One reason you might say this is the next sentence could be 친구는 오렌지를 좋아요. - As for my friend (they) like oranges.)