"They are carrying the apples here."
Translation:Nesou sem ta jablka.
the apples, some specific apples -> ta jablka
"Nesou sem jablka." normally means just "They are carrying apples here."
We may think of a situation where omiting the demonstrative would make sense. It is extremely useful for you to come up with such a context to fully understand the difference in practice.
Usually I am very grateful for all the helpful informatins you give, but this time, I am not convinced. "the apples" in English doesn't refer to some specific apples, like "those apples" would. It is just apples and the problem seems to me that in Czech you usually omit the article while in most other languages you need one.