I worked as a Procurement and Component Engineer at IBM and Lenovo for many years. I can write extremely long informative explanations of the many electronics parts used on circuit boards, but it becomes too much to take in for information. Even this is probably too much, but is the explanation.
There is the base copper, fiberglass, epoxy board that connects everything together. Resistors, capacitors, diodes, and transistors are all single electric function called discretes. The diodes and transistors are single gate semiconductor. All ICs, Integrated Circuits, are semiconductors and have circuit gates equivalent to these diodes and transistors, and can also be a memory which holds a position.
There are cheap low level ICs used as logic and linear ICs. There are memory ICs that hold positions until triggered to change. When these ICs get more and more complicated, they get to millions of gates or the equivalent of millions of individual transistors and diodes and memory. At this level, they are called MICROCOMPONENTS or MICROCONTROLLERS. There is one that controls the keyboard and mouse to take the inputs and process them electronically. A computer has temperature sensors, accelerometers detecting motion, USB input processing, and others of high levels of control.
The main microcontroller is called the CPU, CENTRAL PROCESSOR UNIT, consisting of millions of gates that most electrical signals go through. There is core logic, what used to be called chipset because it was two separate ICs and now is only one.
A video is a set of images and to make those images the millions of LCD pixels need to be directed to change. Millions of little pixels changing up to hundreds of times a second. That function is called the graphics or video controlling. It can be part of the CPU, a separate IC in the same unit package that AMD does for APUs, or a separate graphics microcontroller and that could be on a purchased card.
The complexity of both the CPU and GPU, Central Processor Unit, and Graphics Processor Unit is very high for what it does. That is why they get called Processor Units. They do different things, and are both high end microcontrollers. That is why we can say they are both Processors, but one in the main CPU that almost all signals pass and one just controls the millions of pixels at high speed of change. The CPU tells the GPU what to do. In a gaming PC, you need fast complex ones of each. The GPU creates each image, and CPU is telling the GPU how to create each image.
I hope I went just far enough to understand without getting too difficult. Electronics takes years to learn.