This is a unique two-cell AAA battery holder built specifically for the micro:bit. The 6" (~150mm) cable has been terminated with a JST-PH connector.
The connector mates the JST socket on the micro:bit perfectly, allowing you to easily make your project battery powered.
Note: Please keep in mind that JST connectors are not suited for constant and repeated removal and insertions and may wear out over time. Please use the included on/off switch!