Net
Beginner
One connection in the chip’s parts list: a group of pins that must all be joined by wire.
Novice
A set of two or more pins that must be electrically connected: usually one output pin that drives a signal and the input pins that receive it. A chip has one net per signal, and routing turns each net into metal.
Expert
The unit the router works on. Its pin count (degree) decides how it is decomposed: about half of all nets have two pins, and multi-pin nets are split into two-pin connections along a Steiner tree. Power and ground are special nets, routed earlier by power planning.