The computer is the magic box which everyone holds in their hands today. All computers are built using the same components:

Mother board

The mother board is the component that holds the other components. It's purpose is to allow communication between internal components and to expose ports for external components.

Storage

In order to be able to do anything, you have to have something to do something to, and in order to have that, you need some kind of storage space. Also called computer memory, the storage space comes in many forms, but all of them use binary.

Measuring computer memory

Storage is measured in bits. The bit is the smallest unit of memory, able to hold either a 0 or a 1. To make things easier, standardize, and actually be able to do meaningful stuff, the bits have been grouped into groups of 8, called bytes. After that, the memory scale is done in powers of $2^{10}$. 1 KiloByte (KB) = $2^{10}$ bytes 1 MegaByte (MB) = $2^{10}$ KB 1 GigaByte (GB) = $2^{10}$ MB 1 TeraByte (TB) = $2^{10}$ GB ...

Types of storage

RAM - Random Access Memory

It is the short-term memory of the computer. RAM is fast and ephemeral. It is used by your computer when it is powered on, constantly reading, writing and deleting data from it. When the computer is turned off, everything on the RAM is deleted.

SSD and HDD

SSD from Solid State Drive, it is the successor of the Hard Disk Drive. It is the long term memory of the computer. It is slower than RAM to read and write, but it is not ephemeral. It persists even after the computer is turned off.

ROM - Read Only Memory

Mentioned because of its similarity to RAM, it is memory that once written cannot be changed. Some examples include CDs and DVDs

CPU - Central Processing Unit

The CPU is the "brain" of the computer. It coordinates the other components and is the one handling execution. The CPU has its own small memory called registry.

GPU - Graphics Processing Unit

The GPU is a component built for parallel processing. It is comprised of many (hundreds of thousands) of weak CPUs. Originally created to take care of rendering pixels on the screen, they've become so powerful their uses have been extended beyond that. From matrix multiplication to raytracing to AI, everything is done using parallel processing. The GPU also has its own memory, called VRAM.

PSU - Power Supply Unit

It is the component responsible for delivering power to all the monsters above. That's it. That's all it does. End of story.