The return values are kind of self-explanatory, but I'll give the meaning anyway...
The Value is the EXACT return value you will get in mmb return string.

Value

Meaning

The root path is invalid

This means that a drive under that path doesn't exist

Can not determine drive type

This means that the drive type can not be determined

Removable drive

This means that the drive is a drive with removable storage

Fixed drive

This means the drive is a fixed drive (a local disk)

Remote (network) drive

This means that the drive is a remote (network) drive

CD-ROM

This means that the drive is a CD-ROM drive

RAM

This means that the drive is a RAM drive