Basically a USB adapter is what connects USB-port devices with non-USB-port devices. USB adapter usually has a USB cable on one side and non-USB cable at its other side. To overcome incompatibility issue you just have to plug the correct end into a correct port and the problem is solved.

USB to Serial adapters:

One of the most common non-USB ports is a serial port of course. Even some of the latest computers may have serial ports in order to connect some printers or scanners to them. But the problem may arise when you purchased a new computer with no serial port, but for example need to connect an older printer with serial port to it. In order to connect these two devices you will need a USB adapter.

Wireless USB adapters:

It may sound unusual, but sometimes wireless USB adapter is also used. E.g. when you need to connect wireless keyboard, mouse or headset to a computer you can use a USB dongle that connects to USB port of your machine and doesn't need to connect to anything at the other end. It is also a type of USB adapter that connects USB-port computer with a non-USB device.

Did you know?

Using serial-to-usb or parallel-to-usb adapter combined with USB Network Gate you can share non- USB devices over network.