When we think of stars we usually imagine our Sun. But the simple fact is that the universe is made up of million's of different types of stars. The main types of stars are main sequence, red giants, blue giants, red dwarfs, blue dwarfs, and white dwarfs.
Red and Blue Giants
In astronomy the blue giant is a hot star whose luminosity can either be classified as a giant or as a bright giant. In the standard Hertzsprung-Russell's diagram these stars lie above the right of the main sequence stars.
A red giant is a very large star of high luminosity and low surface temperature. Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion.
Red, Blue and White Dwarfs
A red dwarfs is a small relatively cool star on the main sequence.
A blue dwarf is a predicted class of star that develops from a red dwarf after it has exhausted much of it's hydrogen fuel.
A small very dense star that is typically the size of a planet. A white dwarf is formed when a low-mass star has exhausted all of it's central nuclear fuel and lost it's outer layers as a planetary nebula.