system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What really happens when i push the power button on my computer?
gpt
When you push the power button, an electrical signal is send to the motherboard, and something called POST (power on self test) happens, this is possible because a CPU once is powered it becomes nothing but a little machine that receive orders sequentially, so the only real problem is to send it the first instruction, the first instruction contains the direction of the second instruction an so on.

This signal does that, force the CPU to load the first instruction from ROM Memory (a memory that does not erases after you turn off the computer) that contains that first instruction and CPU starts reading that, this is what is called the BIOS.

The BIOS work is to discover all pc components(RAM, all your video cards and usb, hard disks, keyboard etc) by routines.

Once bios made an index of what the computer has, it reads an specific location of the hard disk where your operating system, like Microsoft Windows, starts and BIOS transfers all the data it recollected and the control of the computer to the operating system.

At this point Windows check what bios said your computer was and start charging their own routines to manage that devices, what ppl often call drivers, and Windows starts. :)