An Earth wire is a wire that goes into the ground to disperse with electricity that excess electricity goes through to prevent a circuit from frying itself. These are very commonly used for dispersing lightning that hits an electrical wire and put it back into the ground where the electricity disperses and is no longer harmful to electronics or people.
 
An earth wire is literally a wire that goes down into the earth – also known as an "earth ground."
It’s meant to be the electrical path that unwanted electricity (such as lightning or a short-circuit) finds easiest to take.
IEC60027
Conductor: Copper
Insulation: PVC
Section:1.5mm2 2.5mm2 4mm2 6mm2, 16mm2, 25mm2, 35mm2, 50mm2, 95mm2, 120mm2, 240mm2