The statement which says that a graph is complete means an undirected graph whose every pair of vertices is connected by an particular edge or unique edge.
An undirected graph is a graph whose edges soea not contain any direction means to which vertex they are directed.
A complete graph has an edge between every pair of vertices that exist in that graph.
Explanation: The first step is to make a goal. The second step is to plan how you will accomplish you goal. The third and final step is to accomplish your goal.