A Directed Acyclic Graph (DAG) is a type of data structure that consists of nodes connected by directed edges, where each edge has a direction. In a DAG, there are no cycles, meaning you cannot start at one node and follow the directed edges to return to the same node. This property makes DAGs useful for representing relationships where order matters, such as in scheduling tasks or organizing data. DAGs are commonly used in various fields, including computer science and project management. For example, in blockchain technology, DAGs can enhance transaction efficiency by allowing multiple transactions to be processed simultaneously, unlike traditional blockchain structures that require sequential processing.