The interplay between discreteness and nonlinearity leads to the emergence of a new class of nonlinear excitations, viz. discrete breathers. These time-periodic and spatially localized excitations correspond to generic exact solutions of the underlying nonlinear lattice models. Discrete breathers are not confined to certain lattice dimensions, nor are they sensitive to the particular type of nonlinearity in the system. They are usually dynamically and structurally stable and emerge in a variety of physical systems, ranging from lattice vibrations and magnetic excitations in crystals to light propagation in photonic structures and cold atom dynamics in periodic optical traps. Basic properties of discrete breathers, including spatial localization and stability, are briefly discussed in this chapter. Special focus is placed on a subclass of dissipative discrete breathers. Dissipation eliminates extended waves and allows for various resonances of discrete breathers with damped cavity modes. We discuss applications of the discrete breather concept in systems where dissipation is not only unavoidable but essential in order to observe and manipulate discrete breathers, and in order to use them for spectroscopic tools, amongst others.