The kernel is the heart of the operating system. The programming code in the kernel is specific to the processor in the computer because the kernel talks directly to the processor. The kernel has some built-in commands. These built-in commands are very basic to the operation of the system. Once the kernel has been compiled, we find the utilities at the next layer.
Utilities are collections of programs that do work.
A utility can take the form of a simple program, like a command or a more complex program, like an application. Utilities are not processor-dependent, like the kernel. A binary is the executable form of a program. Last but not least is the outermost layer, the shell. A shell is a user interface.