GIS networks consist of interconnected lines (known as edges) and intersections (known as junctions) that represent routes upon which people, goods, etc. can travel.
The object traversing the network follows the edges, and junctions appear when at least two edges intersect.
Junctions and edges can have certain attributes affixed to them that increase the cost of traveling in the network, known as impedance. For example, a road network can have speed limits attached to the edges, and a junction can prevent left turns.