The term ground has been defined under VDE 0870 as the totality of the interconnected metal parts of an electrical device.
The potential equalization between different components, circuits and modules takes place via the interconnected metal parts - this can be the chassis or the housing. The ground forms the reference potential for all circuits and systems. In circuit terms, a distinction is made between signal ground, chassis ground and ground.
The ground reference of the individual cables, circuits and modules is connected to each other via ground lines at a reference point. The current flowing via ground can lead to small voltage drops between different ground points and to interference couplings.