What are these amazingly beautiful pictures that are displayed on this post, I hear you ask?
They are called Nebulae (or Nebula, singular) and are clouds of gas floating in space that are made out of dust, hydrogen, helium and other ionized gases. Essentially you are looking at clusters of space debris that eventually form stars. Gravity causes the debris to collect and attract more material. With large formations, the ultraviolet radiation given off by the collapse of material is strong enough to ionise the surrounding gas, making visible in the visible light spectrum. This is what we’re seeing!
The material which is left over after the making of stars is thought to collapse and make planets.
Nebulae can also be created in other ways, including the after-effects of a supernova event (when a really big star dies and explodes). The Crab Nebula is one such example of this.
Tip: you can easily find images like these on the web (Google images: nebula) and they make great wallpapers!