The られる/～える form is called the potential form. Means “can do (verb)”.

食べられる = can eat
飲める = can drink
飛べる = can fly
et cetera.

What makes it confusing is that for る-verbs, the passive form is exactly the same (for う-verbs it’s V-neg+れる – for example, 飲まれる). And what makes it even more confusing is that passive-voice – as you noticed – is a way of doing polite active-voice, because it’s indirect, and indirectness is polite in Japanese. And then there’s indirect passive, which is a whole extra can of worms that I still don’t quite understand myself.

(Incidentally, for る-verbs in potential form, you can drop the ら in casual usage only – 食べれる.)

In the end, it’s just context that lets you tell them apart. You should not, at TextFugu level, be encountering too much passive-as-polite sentences, so mostly you need to be able to tell the difference between potential and passive. It’s pretty much particles that are going to help you here:

ボブさんは日本食が食べられます = Bob-san can eat Japanese food.
日本食はボブさんに食べられます = Japanese food is eaten by Bob-san.