GRUB supports environment variables which are rather like those offered by all Unix-like systems. Environment variables have a name, which is unique and is usually a short identifier, and a value, which is an arbitrary string of characters. They may be set (see set), unset (see unset), or looked up (see Shell-like scripting) by name.
A number of environment variables have special meanings to various parts of GRUB. Others may be used freely in GRUB configuration files.