Wifi signals are invisible to the human eye. There are devices we can use to measure the signal and to determine their strength as well as other characteristics. Using a device to see information about wifi signals is a function of which domain?
WiFi signals are transmitted from a router, send data in packets upstream and downstream, use bandwidth and throughput, and have security measures with all sorts of other technical terms. However, when you want to watch Netflix all you want to see is full bars. This form of abstraction takes all the technical jargon, and give you an easy to understand symbol.
Tap the Abstraction link above to learn more about it!