All motorhomes come with a 12 volt electrical system, but will also need a mains connection. To connect to the mains on a campsite you will need a 16amp orange cable with 3 pin blue external connectors, usually available in 10 or 25 metre lengths.
You will most likely need a home connection which has a short cable with standard 3 pin household plug on one end and external female connection on the other end which hooks up to the mains lead. When connected to the mains, the leisure battery is being charged, while the 12V system is effectively being operated by the mains supply. In general the mains supply is not connected to the engine starter battery.