In graph theory, a graph is a series of vertexes connected by edges. In a directed graph, the edges are connected so that each edge only goes one way. A directed acyclic graph means that the graph is not cyclic, or that it is impossible to start at one point in the graph and traverse the entire graph. Each edge is directed from an earlier edge to a later edge. This is also known as a topological ordering of a graph.

A spreadsheet may be represented as a directed acyclic graph, with each cell a vertex and an edge connected a cell when a formula references another cell. Other applications include scheduling, circuit design and Bayesian networks.

In computer science and mathematics, a directed acyclic graph (DAG) is a graph that is directed and without cycles connecting the other edges. This means that it is impossible to traverse the entire graph starting at one edge. The edges of the directed graph only go one way. The graph is a topological sorting, where each node is in a certain order.

Source: https://www.techopedia.com/definition/5739/directed-acyclic-graph-dag