The type of switch usually talked about with regard to streaming is one that allows the musical bits through but not the electronic noise that comes along through your wifi system (cable into your home and wifi router). Some switches offer galvanic isolation, others turn the electronic signal into light transmitted by Toslink cable. The diehards use several of each kind of switch to get best results.
I'm sure someone who knows much more than me will chime in, but that's my basic understanding of what's going on.