USB is the most common bus used to connect a huge variety of external devices to PCs, laptops and servers. It is not only used by peripherals such as keyboards and mice, but also storage devices such as external drives, smartphone and tablets and more.
These have been several generations of USB since its launch in 1996, each delivering increasingly better performance. These include USB 2.0 up to 480Mb/s, USB 3.0 up to 5Gb/s, USB 3.1 up to 10Gb/s, USB 3.2 up to 20Gb/s and USB 4.0 up to 40Gb/s. USB-A type connectors are used up to the USB 3.1 standard, from then on being superseeded by the smaller USB-C connector in later standards.