What is the difference between a nebula, quasar and red giant?
A Cloud of Dust and Gas. Second Stage of a Star and a Black hole.
A nebula is simply a cloud of rotating dust and gas that is moving in space. The nebula when in contact with a gravitational event like a exploding star will give birth to Stars like our Sun. Nebulas are usually formed from death of a normal sized Star.
A Red-Gaint is a Star. When a main sequence Star like our Sun consumes it's primary fuel (Hydrogen). It rearranges it self, core shrinks and outer layers expand thus making it bigger and lower in temperature. Since the temperature is related to the color of a Star it appears red hence, a Red-Giant. Stars much more hotter than our Sun about 10000 degrees will appear blue.
Quasar stands for Quasi-Stellar radio source. They are usually powered by black holes. A Quasar is generally a Super massive black holes that feeds on the objects near it. Quasar is so bright and Luminous that if it is placed in the orbit of Pluto, it will evaporate Earth's Oceans in quarter of a second.