Because Polish is so much easier than English! (Okay, okay, maybe not, once you start talking about verb aspect, but nonetheless, it's worth pointing out amidst all the people complaining that "Slavic languages are so hard!" that no, in reality they've got a lot of things that make them easier, but sadly those traits often get ignored/overlooked by language learners)
There is no a/the in Polish. If you're translating to English, you'll have to tell by the context.