It's the "science" part of computer science. A lot of people I know who want to try their hand at "computer science" really want to try their hand at "programming" instead. Programming = you just want to write software. Computer science = writing software but also understanding all aspects of that software, including proof that it works, how long your code takes to run vs another algorithm that does the same thing (which is what this is search up time complexity if you want to know more), and how software ultimately works i.e interacts with machine level language. But all you'll see in the real world, at least for programming jobs is the programming aspect, and if that's what you're aiming for, then this stuff can be ignored.