VNC stands for Virtual Network Computing, which is a set of cross-platform software that allows remote access to your machines desktop, even from within a browser under some configutations.
If you can remember Siamese RTG, its a similar concept but supports more platforms (a bit less integrated and slower too).
ViNCED on the other hand, is as you say, a replacement shell environment. I don't use it myself (I think it comes with 3.9 tho), being a hardened KingCON fan, but from what I gather it's the doggies doodads compared to the normal shell. So maybe you'd be better off keeping it ;-)
