Cubase is a "Digital Audio Workshop". In short anything that you need to give your music the final touches it needs for performances etc. Personally, I hardly use the computerised version since I have most of it in hardware form. But when I write music in notation softawre it is easier to just run in through the DAW.Is Cubase a modernized version of the old DOS QBasic or just something completely different?
Cu-basic if I recall (I am not that clued up on Softwares so bear with me) was replaced by visual basic I think with windows 98. Zed would actually be the best person to answer that one but if I am right, Cu-basic was a programming language (Similar to Python) where Cubase is music creation and editing software.
Edit: This might make it clearer. English is my 2nd language so struggling to explain. Sorry