I was confused about this also. I'm just learning Polish but what I've figured out is Oni chodzą = they walk (this is something they do often, but maybe not right at this moment) Oni idą = they are walking. (they are in doing this now)
If I am wrong, will a native speaker please correct me?
I'm not a native Polish speaker. I am American. The only nasal sounds we have in English are 'm' and 'n'. Polish has these sounds, and also the nasal 'e' and 'a'. You can get almost perfect Polish pronunciation if you just say 'e' or 'a' , but let air escape through your nose (A nasal vowel). We don't have anything like this in English. The closest we have is 'om' and 'on' as in 'dawn'. So actually, hearing 'om' is the closest to what we English speakers hear in English.
Duolingo, why do you mess everything? Previous excercise: Chodzę do szkoły - I am going to school Current excercise: Oni chodzą - They are going (Incorrect!! it's Walking!)
I know there are things to take into consideration, such as if it is dinamic or not dinamic, if it is just walk, or by transport, but putting same verb in one example and in other example with different definitions, not cool at all.
The only reason for which "Chodzę do szkoły" could accept "I am going to school" (and it actually did not accept it when you wrote your comment) is that the native speakers seem to mix the tenses in the school context. In any other context "I am going to X" would not be accepted for "Chodzę do X".
"Oni chodzą" is either "They go" or "They walk" and sometimes "They are walking" if it's 'walking around, no destination mentioned'. Like here. But "They are going." would need to be "Oni idą".
Just so we're clear, I don't believe that verbs of motion have been introduced well in this course, but we deal with what we received.