White dwarfs: intrinsic properties and applications

White dwarfs are among the most exotic objects in the Universe. In this talk I will start explaining what white dwarfs are, how they evolve and why they are important. I will then describe the most striking properties of white dwarfs. Special attention will be given to the observed features of the mass distribution, which will be analysed within the context of our theoretical expectations. Finally, I will give a few examples on how white dwarfs can be used as excellent tools for constraining several important problems in modern astrophysics.