In its most basic form, a **graph** is a network made of vertices and edges that connect them together. This basic form can be formally called an **undirected simple graphs**. Formally, we could define it as being $G = (V, E)$, where $V$ are the sets of vertices (also called nodes or points) and $E \subseteq \{\{x,y\}|x,y \in V \text{ and } x \neq y \}$.