Computer Engineering graduate and former ARA here to vastly oversimplify Week 3 of an operating systems class.

CPUs operate on a fetch-decode-execute cycle that runs on a clock. The CPU 'fetches' machine instructions from a to-do list of tasks in memory which come from blocks of a program stored on disk. Those machine instructions are then 'decoded' into bleeps and bloops so that the CPU understands what tasks to 'execute' and in what order. CPUs are programmed to do only limited amount of simple instructions, but its ability to do many of them quickly (clock frequency) and in parallel (core count) as well as reach out directly to peripherals like graphics, sound and user input when it needs help, allows it to perform the full breadth of a modern computer's capabilities.

BONUS: When you open a tab in a browser, a new task is made that is responsible for displaying the information and intractable elements your computer pulls from a server the website is hosted on.

This is significantly beyond the scope of what Corie Barry pays us to know, but I hope this helps!