Is there a way I can see if someone in the house is torrenting videos?

I noticed last week that he set up the new internet service in a home network and that the settings were set that things coudl be shared or seen by the other computers. Today I see that when I open "computer" that there is listed on my network setting his pc, my pc, and his media device. What does that tell me? and I changed the settings so this is a public network. please I cannot het anuwhere to help me understand