What is virtual accounts
 

Am doing research on virtual accounts as compared to shell so needed help on the info or any url that can help in that direction

Most likely depends. A virtual account on a *nix based system usually means its an account that is not local to the system, or that it authenticates against its own passwd type file.

Basically say you have a system and you setup a mysql database for users for the ftp daemon running on the machine since you don't want actual unix accounts locally in the passwd and group files, that would technically be a virtual user to the system.