USB stands for Universal Serial Bus but it is not universal or just serial or a bus. All the different names and numbers make USB announcements read like fake news.
USB is allowed to wallow in out of dateness until some competitor produces an improved alternative then USB jumps in with a catchup, sort of like the iPhone annual update to make it more like a Samsung Galaxy.
A serial bus would have everything flowing on one wire pair. USB uses various combinations of multiple wire pairs plus it transfers power to run devices and power to charge devices. USB requires "hubs" and other logic, most of which is outside of the serial transfer of data.
USB is more like a system with all the fancy chips and complex logic. The only part that is a bus is the cable. Fortunately there is no logic in the cables. They can be as cheap as the copper wire inside.
What is the weird number system? USB 1 became USB 1.0, 1.1, and 1.2. USB 1.2 was renamed USB 2.0. USB 3.0 arrived with more speed then USB 3.1 arrived with double the speed of USB 3.0.
Wait, USB 3.1 is not double the speed of USB 3.0. When you see USB 3.1 on a device, you are almost certainly seeing the cheaper "USB 3.1 gen 1" which is just USB 3.0 with a fancy new name. To actually get the new improved USB 3.1 speed, you have to look for USB 3.1 Gen 2.
USB 3.2 is the current newest and most improved USB. BUT! You have to get USB 3.2 Gen 2x2 to get the improved 20 Gbps speed. If the label only has USB 3.2, it could be the slower USB 3.1 Gen 2 with the fake new label that might be described as "USB 3.2 gen 2" in the fine print or it could be the obsolete USB 3.0 with the fine print description of "USB 3.2 Gen 1".
Thunderbolt is one of the distracting competitors. Intel developed Thunderbolt. Intel improved Thunderbolt into Thunderbolt 3 by using the USB Type C connector. Having copied USB, Intel donated Thunderbolt 3 to the USB group. USB4 is the merge of USB and Thunderbolt 3. Note that it is USB4, not USB 4.
USB4 uses only the Type C connector, not the Type A connector. USB4 will work at USB 3.2 speeds with USB 3 cables. You need new cables to get the higher USB4 speed.
USB4 can transfer up to 100 watts through the right cable which will let the USB4 port replace the mains power charging socket. You could have the power supply run into a USB4 hub then plug the hub into your notebook using a single cable. The hub could have your external monitor, mouse, keyboard, backup disk, and wired network connection all plugged in permanently. Finally a USB to fix that problem.
USB could easily go faster using fibre. Every time they make the copper wire faster, they have to make it more expensive and shorter. Fibre would be instantly ten times faster and cables could be a hundred times longer. The power transfer part could use copper wire of any thickness, removing the length limitations.
We will probably never see it. I proposed exactly that combination to one of the major brands back in the early 1990s when the first plastic fibre optic material arrived. They bought the idea but never did anything because that is what big corporate America does best.
USB4 should arrive before USB 3.2 because so many manufacturers can just relabel the Thunderbolt 3 version of USB Type C stuff. Intel already has the base code in chips, removing most of the code from the operating system. If you are not in a hurry to buy a new machine, wait till the middle of 2020 when every intelligent brand will have some Intel based models with USB 4. All the others will stick with USB 3.1 Gen 2 or USB fake n.n. Two USB 3.1 Gen 2 ports are as good as on USB4 port.