The OS Loader

The OS loader is operating-system specific.

Because of its limited size, the OS loader normally loads another loader (from some place on the active partition), which does the actual loading of the OS.

LILO's secondary OS loader, for example, is responsible for uncompressing the kernel in memory.

Loadlin, in that sense, is not an OS loader. Rather, it is a normal program that just happens to load the linux kernel and pass some standard parameters to it, during startup.