[Mystake]

how do computers decide which one to use?

I'm not talking about being hardwired AND wirelessly connected to the same router, but more like my desktop which has dual ethernet ports and having two separate modems plugged into it.

Even more so, what about when a smartphone is tethered? My phone comes up as an ethernet connection when tethered via USB.

I've always wondered, specifically about the two modems but I've never figured it out cause I never had two internet connections at the same time. I also just got the phone and just found how it shared connection when i plugged it in earlier tonight.