The interface is based on the WCH CH376 chip and allows access to USB mass storage and other USB devices on CPC.
The CH376 chip implements FAT32 in hardware, which means no filesystem driver is needed on the CPC side. It also implements the lower level aspects of USB, making it relatively easy to write drivers for other USB devices (mouse, joystick, ...). It is simple enough that the mouse driver was initially written completely in BASIC.
The Albireo USB port can drive any USB peripheral, including any standard USB mouse. It is no more needed to dig out a PS/2 compatible mouse for your [[Symbiface II]], or even worse, an Atari/Amiga one for the [[MultiPlay]].