In electrical engineering, a ground plane is an electrically conductive surface, usually connected to electrical ground.
The large light-green areas on this printed circuit board are the ground plane
In electrical engineering, ground or earth may be a reference point in an electrical circuit from which voltages are measured, a common return path for electric current, or a direct physical connection to the Earth.
A typical earthing electrode (left of gray pipe), consisting of a conductive rod driven into the ground, at a home in Australia. Most electrical codes specify that the insulation on protective earthing conductors must be a distinctive color (or color combination) not used for any other purpose.
Metal water pipe used as grounding electrode
Busbars are used for ground conductors in high-current circuits.
3 ply static dissipative vinyl grounding mat shown at macro scale