Universal Serial Bus (USB) is an industry standard which was developed in the mid-1990s to standardize the connection of computer peripherals to computers.
Being the most popular and common connector type now it replaced a lot of earlier interfaces.
USB Type B connectors, officially referred to as Standard-B connectors, are square in shape with either a slight rounding or large square protrusion on the top, depending on the USB version.
USB Type-B connectors are supported in every USB version, including USB 3.0, USB 2.0, and USB 1.1. A second type of “B” connector, called Powered-B, also exists but only in USB 3.0.
A male USB Type B connector is called a plug while a female connector is called either a receptacle (as used in this article) or port.
Type-B cable is mostly used for printers, scanners, optical drives, floppy drives(obsolete) and hard drive enclosures.
USB Type B plugs are typically found at one end of a USB A/B cable. The USB Type B plug fits into the USB Type B receptacle on the printer or another device, while the USB Type A plug fits into the USB Type A receptacle located on the host device, like a computer.
The USB Type B connectors in USB 2.0 and USB 1.1 are same, which means that the USB Type B plug from one USB version will fit into the USB Type B receptacle from both its own and the other USB version.
USB 3.0 Type B connectors are a different shape than previous ones and so the plugs do not fit in previous receptacles. However, the new USB 3.0 Type B form factor was designed in such a way to allow previous USB Type B plugs from USB 2.0 and USB 1.1 to fit with USB 3.0 Type B receptacles.
In other words, USB 1.1 and 2.0 Type B plugs are physically compatible with USB 3.0 Type B receptacles, but USB 3.0 Type B plugs are not compatible with USB 1.1 or USB 2.0 Type B receptacles.