A library that provides many usefuk low-level functions to GTK and GDK? programs. This is the C library used by many Gnome programs and forms a basis of GTK+.
In practice it is a very useful library when writing a C program; a lot less re-inventing the wheel needs to be done if you use GLib.
Contrary to popular belief GLib has no dependancy on GNOME or GTK, and is designed for use as a standalone extension to LibC?