Yes - in English, we use the gerund form if the action is current and continuing ('we are buying towels' - ie, right now, that is what we are doing) and the simple present tense if we do the thing as a matter of course (I play golf - ie, not necessarily right now, but typically). My sense (mainly from DL) is that Italian often uses the simple present for the first purpose, and the gerundio to emphasize that the action is happening right now (eg, Sto acquistando = I am shopping - ie, right now). However, I'd love to have a native Italian speaker confirm this suspicion.
Actually, I think you mean present participle, not gerund. They are the same word, but used differently. A gerund is a form of a verb as a noun. "We ARE BUYING towels is using BUYING in the present participle form. My understanding is that Italian doesn't have a present participle tense, but that the simple present tense can be used to mean "we buy" or "we are buying." "BUYING towels can be fun" uses the same word as a gerund -- BUYING here is used as a noun.
In Italian 'we are buying' can be expressed in the present progressive tense as 'stiamo comprando'. It is a specific use of the gerundio that Antony mentions above. More on progressive here:
I've finally chosen the shortest form to type, which seems just fine to me under the given circumstances, although DL has been accepting other forms such as "Let's buy" and/or the continuous form .
I've also come to understand DL gives us a very good, simple progressive pattern of learning to speak. The purpose at the moment isn't too specifically focused on translation, as that would require a context and understanding (which anyhow computers really can't master, fortunately!).
So it's much quicker and efficient to just play the rules of the game, and stay focused on learning!
When I do come to report something, I've had the pleasant surprise of receiving a message accepting it and thanking me!
Asciugamani is not just "hand-towels", but "towels" in general.
(So, it could be used for "bath towels" too.)
If you want to specify that you want "bath-towels",
you'll ask for asciugamani da bagno.
Could this have happened when your exercise was to choose out of a word-pool?
There is no reason for it to have happened in "free writing".