Is there a good breakdown for this? I Guessed "It is raining" but I'm not sure why it's correct.
雨 Rain が (Object particle) ふります (falls)
Note: ふる is only used on rain, snow, etc.
Just like other verbs the simple form talks about an action, and the continuous form talks about a state. Furu is not an exception. I think it is pretty safe to use the same form as you would do in English, though not in 100% of the cases (which I haven't thought of now).
I tried 'rain is falling' and 'rain falls', duolingo won't accept either. Guess they just want you to say 'it rains'
I was reading the comments and I read a lot people translated this as it as "The rain falls". That's not how you would say that it's raining in English generally, right?
Correct. The normal way to say it's raining is "it's raining." The references to "falls"/"falling" are attempts to get as close as possible to the Japanese sentence, I suppose. "The rain is falling," for example, is basically interchangeable with "it's raining"; it's just a touch more poetic, and I think I would tend to use it when I observe a forecast rain to be starting.
There must be a difference in usage. "It is raining" is accepted (as is "it is snowing" for the analogous sentence).
I assume Japanese folk don't always use the simple present form for currently falling precipitation, but it would be nice to know details.