The backend does what a station cannot do on its own.

A charging station on its own can do little. It switches current, measures it and reports its state. It knows no cards, keeps no list and bills nothing. Its job ends at the terminal block.

The backend does the rest. It holds the cards and the permissions, answers every request a station makes, records each session with its meter readings and shows which station is charging and which is idle. It is the only place where the installation becomes visible as a whole.

The sequence is always the same: the driver holds a card to the reader. The station asks the backend. The backend answers yes or no. The station releases the plug or flashes red. The whole exchange takes the blink of an eye.

Then there is the administration. Adding stations, keeping organisations and users apart, setting a price per kilowatt hour, producing reports, raising faults: all of it happens in the backend. The file the finance team needs at month end is made there too.

Almost every wallbox manufacturer runs a backend of its own and sells it as a subscription alongside the hardware. OCPP lets you connect a backend of your choosing instead. The station simply points at a different server address. The switch takes minutes per station.

The backend decides what you see and what you bill from. It holds your charging data and your list of users. That choice ties you down for longer than the choice of hardware. Two questions are worth asking early: where does the data sit, and can you get at it if you need to?