CompiledFunction[args...] represents compiled code for evaluating a compiled function.
Compile generates a CompiledFunction object that can be executed by applying it to appropriate arguments.
CompiledFunction objects that are constructed explicitly can also be executed. Basic consistency checks are done when such objects are first evaluated by Mathematica.
The code in a CompiledFunction object is based on an idealized register machine.
A CompiledFunction object can additionally refer to natively compiled code.