Linux may boot using different mechanisms. Booting involve mainly reading and bringing a kernel file (often called zImage or vmlinuz) in memory, then laughing it. While this sounds all simple, there is always some quirks around. This is why booting an Operating System is some sort of black art. Unlike many boot loader shipped with some other commercial OSs, LILO is fully documented and probably the most versatile loader ... by far.
We will first try to describe what's involved and then what you can do with all that.