Some formal aspects of supersymmetry breaking are reviewed. The classic "requirements" for supersymmetry breaking include chiral matter, a dynamical superpotential, and a classical superpotential which completely lifts the moduli space. These "requirements" may be evaded in theories with large matter representations. The mechanisms of supersymmetry breaking by confinement and quantum deformation of the moduli space are explained, with emphasis on the importance of identifying the relevant degrees of freedom in the ground state. Supersymmetry breaking and the behavior of the Witten index in non-chiral theories are discussed. The quantum removal of directions which are classically unlifted is also illustrated. Examples of product gauge group theories that admit dual descriptions of the non-supersymmetric ground state are also presented.