Gas discharge phenomena occur when an electric current passes through a gas, causing it to ionize. This process creates charged particles, which can lead to the emission of light, as seen in devices like neon signs. The behavior of the gas changes under different pressures and voltages, influencing the color and intensity of the emitted light. These phenomena are essential in various applications, including fluorescent lamps and plasma displays. Understanding gas discharge helps in developing technologies such as gas lasers and ion propulsion systems, which rely on the manipulation of ionized gases for their operation.