A directed graph is a network of nodes and connections (often called edges), where each edge has a direction. This is rather like a city with a one-way system. For example, a graph with three nodes A, B and C, might have the following dirceted edges: A→B, B→A and B→C. Note how there are links between A and B in both directions; there is a link going from B to C, but not the other way round; and there is no link at all between A and C. Directed graphs often arise in games where moves take one from one gae state to anther, but often are not symetric; so that you can't always reverse your last move.
A directed graph is in contrast to an undirected graph where edges have no direction and effectively link both ways.
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