Translation:What kind of mushrooms are those on the table?
Fun fact: In Greek (my native tongue), you can use a similar syntax to ask this type of question, but it sounds very rude.
"Τι είναι αυτά για μανιτάρια στο τραπέζι;" Ти Инэ афтА я манитАрия сто трапЭзи? (for anyone interested in the pronunciation, since most of you studying this course probably know how to read in Cyrillic at this point)
This is pretty much a word-for-word translation from Russian that's still valid in Greek, but it conveys a different meaning. It's more like "What the f**k kind of mushrooms are those on the table?!" So you use it, in a rude way admittedly, if you see some really weird mushrooms or you want to bash someone's cooking skills. :D
Just wanted to share why I always chuckle when I encounter this particular type of questions in Russian.
When used with the accusative case, за can also mean ‘for’, just as для can mean ‘for’ when used with the genitive case. Recently, I got corrected for writing ‘Большое спасибо для вашего ответа’ (‘Thank you very much for your answer’), instead, it should have been ‘Большое спасибо за ваш ответ’.
If you want to convey the meaning of ‘for’ like in the above mentioned example, when should you use за + Ack. and when should you use для + Gen.?