In this thesis, we consider supersymmetric domain walls of four-dimensional N=1 super-QCD for the simply connected gauge groups Sp(N) and SU(N). First, we construct the BPS domain walls numerically when the number of flavors F=N, N+1 in the SU(N) case, and F=N+1, N+2 in the Sp(N) case.
In the second part, we discuss some proposals for the low energy descriptions of the physics on the domain walls. These proposals pass various tests, including dualities and matching of the vacua of the massive 3d theory with the 4d analysis. However, our analysis is partially successful in some cases. In those cases, we suggest that new purely quantum phenomena are needed to properly describe the low energy physics.