Don Smith asks a wonderful leading question on networking in OS X:
I have an ethernet connection to my FiOS modem/router and it works great. Somewhere along the line I had to turn on my WiFi as well. Don’t remember why. Just curious, is it a benefit or a deficit or is it neutral to have both connections active at the same time?
Don (and Don really exists, I didn’t invent him, I swear), that’s a great area to discuss. OS X is a well-designed modern operating system that for many releases has let you have multiple active network interfaces. They can be “real” in the sense of directly corresponding to physical hardware that’s part of or attached to a Mac, or “virtual,” as is the case with VPNs (virtual private networks).
Read more here:: Can you use Wi-Fi and Ethernet on a Mac at the same time?