What is the tangle?
“A revolutionary new blockless distributed ledger which is scalable, lightweight
and for the first time ever makes it possible to transfer value without any fees. Contrary to today’s Blockchains, consensus is no-longer decoupled but instead an intrinsic part of the system, leading to decentralized and self-regulating peer-to-peer network.” - iota.org
Learn more on the official IOTA website.