I just typed it in. You do not have to use the word bank, you can type your own answer. In my opinion you are lerning more by doing so.
I suspect it is along the lines of, especially in arguments, "What do you really mean, what do you really want to say?" Where someone has said something possibly ambiguous, possibly offensive, and someone is asking for clarity. Or raising the level of the argument.
I found several places that said it is regional. Here is one https://dante-learning.com/eng/che-cosa-or-che-cosa-the-italian-way-to-say-what-podcast/
Here is a somewhat related post https://www.duolingo.com/comment/3320936/Qual-vs-Cosa