The connections between vertices are called Edges. An edge connects Vertex to Vertex .
In the map example, a road between two cities is an edge. In social networks, a friendship is an edge. In chemistry, a bond between atoms is an edge.
Edges can carry extra information like weight (distance, cost, time) or direction. Problems often give you a list of edges: "There is an edge between and , between and ." You will learn to store these efficiently. The number of edges affects algorithm speed.