From MEPIS Documentation Wiki
The root of Linux is simply "/". Every directory, file and device stems from this. Some say that this similar to the C: drive in Windows but that is not true. In Windows, C: is a drive. In Linux / is the beginning point for the entire file system. Everything in Linux starts at / and everything can be followed back to it. The "/" contains all of the major directories, and it is generally a bad idea to store files in the "/" directory. Even though "/" is referred to as the root, it should not be confused with the root user.
Some people will refer to the root directory when they are actually referring to the root home folder, which is /root. This is the home directory of the username "root", analogous to the other home directories for users without superuser status. This should not be confused with the system root, which is the directory at the highest level in the filesystem more detail