The cabling from your controller/DJ mixer to the PA/PA mixer is the most confusing, because it can be RCA, TRS or XLR. The main difference is that RCA is an "unbalanced" connector and cable, and that the TRS and XLR variants are balanced. Now a balanced cable will in general be less prone to interference and can carry even low signals over a larger cable length. However many entry controllers only have RCA outputs.