Plasma is a gas that is pumped with energy from an external energy source and as a result of the energy supplied is partially ionized
This means that the electrons of the atoms are released from the respective atom, but the electrons still follow with their respective nuclei. Thus, in a plasma, both ions and electrons exist, which allows electricity to flow through the gas. All atoms in the gas must not have been ionized for plasma to be obtained.
This is what happens when a flash runs through the air.
