This globe of electricity was first discovered by Nikolai Tesla after his experimentation with high frequency currents in a sealed glass tube. He named his creation the "Inert Gas Discharge Tube." This lamp used the high voltage discharge from a Tesla coil to excite an inert gas that resided in the tube which created a streak of light.
A usual globe today is made up of a electrode that is suspended in the middle of a glass globe, which is then filled with an inert gas and sealed at an intermediate pressure. Most of today's globes are filled with xenon gas, but other globes can be filled with neon, argon, krypton or even a mixture of gasses.
So how does the electrode create the plasma inside the globe? Well first we need to apply a voltage to the electrode to create a stable electric field between it and the glass globe which allows the electrons move freely through the gas. Then at the same time we apply a second oscillating voltage on the electrode, the alternating electromagnetic field that this creates is what keeps the electrons moving in the gas. As the electrons gain more and more energy as they move around the globe they iodize the gas which creates the streaks of plasma light. Because of the pressure of the gas in the globe, the collisions between particles become more frequent. As the collisions become more numerous, the ions start to recombine with free electrons and turn the gas back to its unexcited state. This concentrates the electrical discharges into narrow tendrils which creates the light show everyone is familiar with.
So what happens when you pump a whole lot more voltage than your supposed to through one. Well it gets very interesting of course, Give it a watch.