G-H
gateway
A route from a computer to another network. A default gateway address is the IP address of a computer or router that connects a LAN with another network such as the Internet.
getty
A getty is a terminal program, which includes prompts for a login and a password. Virtual console gettys are configured through the mingetty program via /etc/inittab.
GNOME (GNU Network Object Model Environment)
GNOME is the default GUI desktop for Red Hat Enterprise Linux.
GPG (GNU Privacy Guard)
GPG is an implementation of the OpenPGP standard included with Red Hat Linux.
group ID
Every Linux group has a group ID, as defined in /etc/group.
GRUB (Grand Unified Bootloader)
The default boot loader for RHEL 3.
grub-install
The grub-install command makes your BIOS look for your GRUB boot loader.
home directory
The home directory is the login directory for Linux users. Normally, this is /home/user, where user is the user's login name. It's also represented by the tilde (~) in any Linux command.