Over the past decade, blockchains have risen to become the leading form of distributed ledger technology. Despite their current dominance, however, a growing number of projects are proposing alternative solutions to solve certain scalability issues inherent to blockchains. One of these proposed technologies is the DAG, or Directed Acyclic Graph, which has been promoted by a number of alternative layer 1s as a more efficient solution than traditional blockchains. This research report aims to educate readers on alternative layer 1s which use DAG technology, while providing a framework to classify different uses of DAG technology and improving knowledge of how they operate.