What is the difference between a white dwarf and a red giant?

Stars go through several stages in their lifetimes, from birth to death. The two stages mentioned in the question - white dwarf and red giant - are the final stages of different types of stars.

A white dwarf is a small, dense star that is the final stage of a low to medium-mass star. When a star like our sun has exhausted its nuclear fuel, it runs out of the energy needed to support its outer layers, and the core collapses in on itself. This collapse heats the core, causing the outer layers of the star to expand, creating a planetary nebula. What is left is a hot, dense core called a white dwarf.

A red giant, on the other hand, is the final stage of a high-mass star. When a star much larger than the sun runs out of fuel, it undergoes a series of collapses and expansions. The outer layers of the star expand and cool, turning red, while the core contracts and heats up. A red giant is much larger and cooler than a white dwarf.

So, in summary, the main differences between white dwarfs and red giants are their mass, size, temperature, and the type of star that they are the final stage of.