IOTA is the first distributed ledger protocol that goes ‘beyond blockchain’ through its core invention ‘Tangle’. The IOTA Tangle is a Directed Acyclic Graph which has no fees on transactions and no fixed limit on how many transactions can be confirmed per second in the network; instead, the throughput grows in conjunction with activity in the network; i.e., the more activity, the faster the network.
The Directed Acyclic Graph is a specific data structure based on a graph without any directed cycles. Instead of having a single branch with nodes having only one edge, in a DAG there can be multiple branches
Unlike typical blockchain architecture, in IOTA there is no separation of users and validators; rather, validation is an intrinsic property of using the ledger, thus avoiding centralization.