This is a connector that fits directly to the edge contacts of a BBC . The connector has 80 pins, but because of the different widths of the micro:bit edge contacts, some of the micro:bit contacts will map to more than one of this connector's pins. Also, the back half of the pins are not used at all.

The edge connector gives access to all the important pins on the bottom edge of the micro:bit. Check the datasheet for the pin spacing and orientation. This connector is best used with a custom PCB!