WiFi and Ethernet Combined On System

My PC, like most others, has the ability to connect to the net via the wireless or ethernet route. Thinking I knew enough about network connections already, I was proved wrong. It all happened during a speed test of my wireless network. I always noticed that whenever I connected to my wireless network, my ethernet connection always stayed active, it doesn't disconnect. Running speed tests with Wi-Fi active always resulted in the same transfer rates as when I tested with ethernet. Grant that's possible, but not likely. On further investigation and with Task Manager active viewing the comms on the performance tab, I noticed that when running speed tests with Wi-Fi as the connection, it resulted in no transfer of send or receive data on the Wi-Fi connection status. However, the ethernet connection was doing all the transfers. So now I am humbled. Turns out ethernet takes the priority unless you disconnect the cable. Just switching the source has no effect.