The Bitcoin Lightning network protocol was originally proposed in 2016 by developers Thaddeus Dryja and Joseph Poon.
The Lightning Network is a layer-2 solution that utilizes a network of payment channels which are established between two users. Once two users have established a payment channel (a 2 of 2 muti-sig), they can send payments back and forth without broadcasting their transactions to the entire Bitcoin network.
A lightning channel will normally remain open until one party decides to close it, when it is closed the final balances will be broadcasted back to the blockchain. As only the final balances are broadcast, (not all the micro transactions that occurred within the channel) this also adds additional privacy.
To learn more about the lightning network and how it works we have listed links to some fantastic resources below, going from basic to quite technical:
https://letstalkbitcoin.com/blog/post/the-lightning-network-elidhdicacs – (explains lightning using analogy)
https://github.com/lnbook/lnbook – “Mastering the Lightning Network: A Second Layer Blockchain Protocol for Instant Bitcoin Payments” by Andreas M. Antonopoulos (Author), Rene Pickhardt (Author), Olaoluwa Osuntokun (Author)