  The breaking of supersymmetry is usually assumed to occur in a hidden sector. Two natural candidates for the supersymmetry breaking transmission from the hidden to the observable sector are gravity and the gauge interactions. Only the second one allows for supersymmetry breaking at low energies. I show how the two candidates deal with the flavor and the $\mu$-problem; I also briefly comment on the doublet-triplet and dark matter problem. 
Advantages and Disadvantages of Supersymmetry Breaking at Low Energies