TL;DR: The USB Implementers Forum is ridiculously bad at naming, symbols and communication in general. (And they don't seriously enforce any of this anyway, so don't even bother learning it.)
Thank God there's a standard for USB. And another one. And another one. And another one. And another one. And another one. And another one. And another one. And another one. And another one. And another one. And another one....
It's not just USB PD that supports power delivery: Standard USB from way back in 1.0 also supports power delivery to devices as standard, but it's only up to 100mA in USB 1.0, 500mA in USB 2.0 and 900mA in USB 3.0, all at 5V.
USB PD is a dedicated power delivery USB protocol that supports much higher currents (up to 5A) as well as dynamically configured voltages (so, not fixed as 5V anymore) though it's all negotiated so your 5V-only phones isn't going to just get burned with 20V from a USB PD charger.
Since Power = Current * Voltage USB PD can put out quite a lot of power for supporting devices (the maximum depending on what both sides support), which means much faster transmission of power via USB which for example means faster charging of chargeable devices via USB with USB PD.
Anyways, the point being that even really old USB 1.0 can charge your device (just really really slow, though you'll be hard pressed to find anything that doesn't support at least USB 2.0 which can send 5x the current of 1.0 hence charge 5x faster than it), and that standard charging speed goes up with each new Standard USB generation since each has a higher maximum current than the previous one, so for example a standard USB 3.1 charger without USB PD support can still push a nice amount of power down the line to charge devices. It's just that with USB PD things really take off (though only up to a shared maximum that both sides support) and it can push enough power to support larger devices such as full-blown monitors or even charging notebooks.
It gets even better, each function of the port also needs proper support from the cable. Often cables do not support the full spec of usb to cut costs.
While the symbols in the post are often put on computers, for usb cables this is seldom done (only a few brands do).
Source: had to find a cable that supports both DP and PD to connect a portable external monitor after I lost the original cable. (1/9 cables worked)
I just love that in a world with Power Delivery (PD) they decided that the best way to indicate Display Port (DP) was to have an ambiguous symbol involving a P and a D.
The USB standards are just... Comically overcomplicated. And almost everything about it is optional. They need a full revamp, making it simpler and mandatory on all future ports, devices and cables.
The USB-C standard and particularly the USB PD (power delivery) is so complex it almost feels comical.
The PD standard document (freely available on usb.org) is over 800 pages long and features a lengthy part about the role of the cable alone which is mostly hidden from the user. Here's a short video about this issue: https://www.youtube.com/watch?v=6bZ0y9G-4Pc
It's future proof and doesn't need a decoder manual other than basic literacy. It can be in whatever language the fucking keyboard is. If you want to be redundant but even more clear:
Every device I have just has a couple of blue ones and a couple of black ones, perhaps some orange ones and some USB-C ports, and good luck figuring out what they all can do. No symbols anywhere.
Additionally, USB 3.0, 3.1 and 3.2 labels provide no information on the speed. Rather, "Gen 1" means 5Gb/s, Gen 2 means 10 and Gen 2×2 means 20Gb/s. These "Gen" labels are seldom found on products however.
So for example USB 3.2 Gen 1 is 5Gb/s while USB 3.1 Gen 2 is 10Gb/s
The standard might be complicated if you want the specifics, but for everyday use it's incredibly simple, and I love it. The number of times I needed this information is 1, even though most of my devices, including an external monitor, are USB-C.
I think that maybe having two similar lightning bolt symbols that mean different things wasn't the best design decision that the USB guys could have made.
Those will legally do pretty much anything depending on what cable you use anyway. (and what cable you end up using is pretty much a surprise until you've tested it.)
All thanks to USB making our lives more simple. (yay)
Ok, I suppose it is more simple in quite a few ways.
some additional info about USB. If your cable/connector is old, idk how old is requred, the names and standards are actually completely different now than they used to be, but they're adopted into the new standards, so you have to keep this in mind when trying to recognize this stuff.
I can't even find a decent PCIE USB/Thunderbolt card (one that support VFIO would be nice and actually has a Linux kernel driver, so ASM and Renesas are both out..)