Here is a progression of the evolving nature of a planetary or  ring nebula. The phrase "planetary nebula" is a misnomer. When these objects were first observed, they did look a bit like fuzzy planets. That's when they got the name planetary nebula which persists to this day. Through a low power eyepiece the object on the left, called the Snowball nebula, looks a bit like Uranus. The middle picture is called the Saturn Nebula because its size and shape are reminiscent of its namesake Saturn. The classically shaped nebula on the right is called  M57 or the Ring Nebula, an object  large enough and bright enough to be plainly visible with a modest astronomical scope. It is a strikingly three dimensional; seemingly hovering like a cosmic smoke ring somewhere between our earth and the cosmic background.
Actually, Planetary Nebula are cosmic smoke rings. They are created when a star's hydrogen fuel is exhausted and it collapses on itself. That collapse creates enough pressure to ignite helium fusion which in turn causes an explosion that blows off the stars outer layers which we see as the smoke ring we call a planetary or ring nebula.

8" F10 Schmidt Cassegrain Telescope, 40mm eyepiece, Canon G2 between 3x and 1.8x
 F2.0 to 2.2, 15 sec, ISO 400
Approximately 6 to 10 photos of each object were averaged together to get one representative picture, then brightness and contrast of each was enhanced. Size was adjusted to indicate actual relative size to one anothe, and then the composite was put togetherr.