A confusing name as it is far to close to DisplayPort. The most common I've seen is called DisplayLink. There's really only one way to get video from USB-A, a GPU. USB 2.0 is considerably slower than USB 3.0 or TB3.

They work reasonably well for many people, they won't win any prizes for frame rates on gaming or video processing. There are USB 2.0 docks with GPUs in them to get DP and DVI outputs. I have a USB 3 type A docking station at work that outputs DVI and Display Port that I use with my Mac, so I'm aware that my laptop will output video over USB, but I've tried the above configuration and the laptop sees the hub as USB 2.0 and no display is detected. There are micro-USB to HDMI cables that use HDMI natively (though more accurately it's the MHL protocol but it uses the HDMI connector) but these are also rare. USB-C ports that support HDMI natively is possible, it's in the spec, but I have not seen it. Because TB3 was built for adding GPUs they are much easier to setup, fast, and while they are often not cheap they are worth every penny. There are GPUs built for computers that support TB3 on USB-C. Because many laptops with USB-C support DP natively on the port the cables are simple, low cost, fast, and require no drivers. Because these USB GPUs are using a protocol not intended for connecting a GPU they are known to be expensive, slow, and difficult to set up.

USB-A only supports USB 2.0 and USB 3.0, to get video from it means using a USB GPU. USB-C can be used for USB 2.0, USB 3.0, DisplayPort (DP), HDMI, Thunderbolt 3 (TB3), and more. USB-C is independent from the USB 3.0 spec. You can know the difference in that the cables and docks with GPUs will require drivers to work, the cables and docks with DP-to-HDMI protocol converters do not.

There are USB-A to HDMI adapters but they use a GPU, not a protocol converter like most USB-C to HDMI adapters. There's nothing wrong with ignorance except those that do not seek to end it. The reason this kind of an adapter exists is because there are people that prey on the ignorant with cheap fixes to complicated problems.

These adapters have no defined function in the spec and so run the risk of doing nothing, doing what you want and expect, or doing damage to your hardware. An adapter with a male USB-A jack to female USB-C receptacle violates the USB specification. Can I use a USB-C hub with a Type-A to Type-C adaptor to get HDMI from my Early 2015 MacBook Pro with no USB-C port?

Usb hub for macbook 2015