The “Tangle” refers to a blockchain alternative developed by IOTA, the open-source distributed ledger and cryptocurrency. Tangle is a name for IOTAs Directed Acyclic Graphs (DAG) transaction settlement and data integrity layer. The Tangle is a string of interlinked transactions and stored through node participants. 

This alternative blockchain does not have miners that validate transactions. What it makes use of to do so is a network of participants. These participants are required to confirm two transactions that have already been submitted to the network for every transaction issued.  The transaction may be issued to the network with no fees and may also facilitate micropayments. Computational resources based on Proof of Work (PoW) algorithms are required from every transaction to avoid spam. 

As IOTA supports value and data transfers, a second layer of protocol is also provided. Encryption and authentication of messages are transmitted and stored as zero-value transactions on Tangle.