Van/Leisure battery

[MLCE Campers]

Hi new member here, hope I’m posting in the right section. Recently purchased T6 campervan and have the Sargent control panel inside to control the electrics and lights. There is the option to use the van or leisure battery when it’s on, what is the difference between them please? Thanks

 

[RedUn]

The van battery is your starter battery and the leisure is the 2nd battery for camping