Meteor showers are a spectacular phenomenon that takes place when the Earth intersects the path along which periodic comets (or less frequently, asteroidal bodies) orbit the Sun. Comets lose debris when they get close to perihelion, but the debris does not get lost in all directions - it continues to follow the comet s path in the solar system.
When our planet plunges in that gas of particles of all sizes, from ones as small as micrometric specks of dust to ones as large as boulders, a shower occurs. It may last a few hours to full weeks, and it typically reaches a few hours-lasting maximum when the highest density of bodies enters the upper atmosphere, then fading away. Most meteoroids ignite as they reach an altitude of about 100 kilometers, but what we see from the ground is not exactly a combustion. Rather, it is the light emission resulting from the conversion of kinetic energy of the meteoroid as it progressively slows down in the thickening medium.