IOTA is a permissionless distributed ledger "for a new economy". IOTA was conceptualized in 2015 and officially released in June 2017.
It targets the Internet of Things, through the use of an open-source distributed ledger. IOTA aims at supporting the growth of a machine economy by enabling "fee-less machine-to-machine payments", offering greater scalability than blockchain networks.
IOTA relies on the Tangle, which is a Directed Acyclic Graph (DAG). Unlike blockchains, DAGs do not rely on blocks, miners, nor a concept of a chain. Instead, a DAG is a network of transactions that are linked to each other in a tree-shape network.
According to the team, core features include: improved scalability (network activity is negatively correlated with settlement times), low resource requirements, zero-fee transactions, secure data transfers (through encryption), the addition of offline transactions, and quantum immunity.