And, trying hard not to sound patronising, it's the third iteration, after usb a and usb b.
I think there may have been USB b1. 1
Well... not quite. If you think of the old 'printer' cables that are still knocking about, USB A was the 'letterbox' end for the PC and USB B was the squarer end with the chamfered top for the printer. Most cables went A to B, but there was occasionally need for an A to A.
There were also Micro USB connectors of at least 3 different designs used for smaller kit/earlier smartphones.
USB-C is the physical designation of the new small cable that is supposed to blow all of that away, but because of legacy USB-A ports on computers being far more numerous than USB-C we've settled down for a potentially-long transitional period of people using A to C cables (though to be fair my latest company car only has USB-C in it).
To further complicate matters, you also have USB 2.0, USB 3.0 etc, these are the designations of the data transfer rates (how fast you can copy files across etc). It used to make a lot of sense but since USB 3.0 we've moved to:
USB 3.1 gen 1 (this is the same as 3.0)
USB 3.1 gen 2
USB 3.2 gen 1x1 (this is also the same as 3.0)
USB 3.2 gen 1x2
USB 3.2 gen 2x1 (this is the same as 3.1 gen 2)
USB 3.2 gen 2x2
The important thing to know is the x2 designations are twice as fast and are only available in the new USB-C physical connector.
There are even faster speeds available now but the key change is that they still use USB-C as the physical connector, so you can use the same cables for in theory any devices and it will all just run at the speed of the slowest component (the device at either end or the cable itself).