Ionization is the process by which atoms or molecules gain or lose electrons, resulting in the formation of charged particles called ions. This often occurs when a gas is exposed to energy, such as heat or electricity, causing its molecules to become electrically charged. In many cases, ionization transforms a gas into plasma, a state of matter where these charged particles move freely. Ionization is fundamental in fields like physics, chemistry, and electronics, and is essential for technologies such as fluorescent lighting, plasma displays, and certain types of sensors.