You aren't born knowing how to drive a car. Learning takes practice. Once you learn how to drive, you can concentrate on where you want to go. Cars differ, but when you've learned to drive one, you can drive others. They have the same stuff, but perhaps not in the same place.
Computers are much the same.
They come in different makes and models, but they operate in much the same way. You don't need to know about transmissions and carburators to be able to drive a car. Similarly, you don't need to know about CPUs and RAMs to be able to use a computer. The computers we are using today are IBM compatibles running the Windows operating system. You use the operating system to tell the computer what you want to do.