Graph connectivity refers to the degree to which the vertices (or nodes) of a graph are connected to each other. A graph is considered connected if there is a path between every pair of vertices. If a graph is not connected, it is called disconnected, meaning some vertices cannot be reached from others. There are different types of connectivity, such as vertex connectivity and edge connectivity. Vertex connectivity measures the minimum number of vertices that need to be removed to disconnect the graph, while edge connectivity measures the minimum number of edges that must be removed. Understanding these concepts is essential in fields like network design and computer science.