If you get it where you can scroll over individual words and have it pronounce the individual words, it's great practice for hearing the subtle sound differences. This kind of thing comes up all the time in French so it's good to train your ear.
EDIT: Train your ear with more than just DuoLingo though. The pronunciation is off too often to be reliable.
Well, there is a difference but I get the feeling it is the same as the difference between say and speak in English. In this case "They say/they are saying our names" is just as correct as "They speak/they are speaking our names".
Dire (to say) and parler (to speak) are used similarly to their English equivalents so I suspect the reason they marked you wrong is that they gave you the word "disent" and they wanted you to translate that to its closest English match, which is "say". Even though the words are interchangeable in this context, it is kind of like if you asked someone to copy out "they speak to me" and the person wrote "they talk to me", same meaning but the person hasn't done specifically what you asked.
Yes, I'd say they're often interchangeable, BUT:
If you compare this to seeing/watching (voir/regarder), I'd also say there's a big difference between: 'I saw the children.' and 'I watched the children.'
In the saying/speaking example, though, changing the words seems pretty harmless...
Non-english speakers on this board should note that while the words say and speak appear to mean the same thing and can therefore can sometimes be interchanged they often have a different usage in English.
Eg: non-english speakers has a clear, immediate meaning, non-english sayers definitely does not.
What do you say?....I say yes. But not... I speak yes
What do you speak? ....I speak French. But not...I say French.
This particular error makes it look like you think noms is actually feminine plural nomes spelling, which doesn't exist.
Personally, I'm always surprised when Duo allows any spelling mistakes given the few short words in the answers submitted for marking.
I'm a very poor keyboarder so I make plenty of them.
I believe because if you listen closely, you can hear the 's' in 'disent'. You wouldn't hear that if it was "Il dit". Listen to the sentence on Google Translate and you will hear the difference between "dit" and "disent" better. The French robot is sometimes hard to understand. You will not hear a difference between "dit" and "dis" however.