Although a shooting star looks like a star shooting across the sky, it's actually a meteor, or small rock that hits Earth's atmosphere. Because of the speed at which the meteor, or meteoroid, is traveling it burns and releases a glow.
When Earth passes through debris, leftover from a comet orbiting the sun, many meteors burn when they hit Earth's atmosphere, creating what appears to be shooting stars. During certain times of the year, it's possible to observe many shooting stars at once; this phenomenon is also known as a meteor shower. It's also possible that the meteor won't burn completely and instead hits Earth.