LILO (LInux LOader) is a boot loader (a small program that manages a dual boot) for use with the Linux operating system. Most new computers are shipped with boot loaders for some version of Microsoft Windows or the Mac OS. If a computer is to be used with Linux, a special boot loader must be installed. LILO is the most popular boot loader among users who employ Linux as their main, or only, operating system.
When a computer is powered-up or restarted with LILO installed in the usual manner, the basic input/output system (BIOS) performs some initial tests and then transfers control to the Master Boot Record (MBR) where LILO resides. The primary advantage of LILO is the fact that it allows for fast boot up of Linux when installed in the MBR. Its main limitation is the fact that not all computers tolerate modification of the MBR. In these situations, there are alternative approaches for using LILO, but it takes longer.
There are several boot loaders other than LILO that can be used to boot Linux into a computer's memory, such as LOADLIN (LOAD LINux) and GRUB (GRand Unified Bootloader).