Wikipedia
Debian-Installer is an installation program designed for the Debian Linux distribution. It originally appeared in Debian release 3.1 (Sarge), released on , although the first release of a Linux distribution it was used with was Skolelinux Venus (1.0). It is also one of two official installers available for Ubuntu; the other being called Ubiquity (itself based on parts of debian-installer) which was introduced in Ubuntu 6.06 (Dapper Drake).
It makes use of cdebconf (a reimplementation of debconf in C) to perform configuration at install time.
Originally, it only supported text-mode and ncurses. A graphical front-end (using GTK+- DirectFB) was first introduced in Debian 4.0 (Etch). Since Debian 6.0 (Squeeze), it uses Xorg instead of DirectFB.