It is the Science of Computing. Memory Management is a great example of this. You learn the theory behind memory management, physical vs virtual memory, pages, swapping, with the goal of being able to understand how modern computing handles memory. And down at that level, it's all theory and math. You don't actually need to use a computer to understand it. Something like sorting lists at an algorithmic level can be applied without a computer. Part of CS is understanding the most efficient way to sort or traverse a data structure- a computer isn't needed to apply it.

It's like Medicine. You can know how the human body works down to a cellular level without ever touching another human. It's not very useful without another human to apply it to, but the science and application of that science can be two distinct topics.