At the time of writing particle accelerators are beginning to probe the 100 GeV to 1 TeV energy scale at which many theorists expect the first direct evidence of supersymmetry to appear. This chapter shows that super-symmetry implies that all particles possess supersymmetric partners having opposite statistics. This is because supersymmetry multiplets consist of equal-mass particles whose spins differ by 12. The chapter reviews the Poincare algebra, showing that supersymmetry involves the introduction of a spinor generator to supplement the usual generators of the Poincare group. It discusses the supersymmetric field theory and considers the representations of the supersymmetry algebra that can be realized by one-particle states. The most important realization of supersymmetry is in quantum field theory. Supersymmetric field theories permit the solution of the ‘hierarchy problem’, and at the time of writing this is the only known solution.