These three well written articles by Aaron van Wirdum explain BU's 'Emergent Consensus' (spoiler alert - it's got issues)

They are listed here sequentially and I'd suggest reading them in order before diving into the last one directly if you don't already know what EC means.A Closer Look at Bitcoin Unlimited's Configurable Block Size Proposalhttps://bitcoinmagazine.com/articles/closer-look-bitcoin-unlimiteds-configurable-block-size-proposal/How Bitcoin Unlimited Users May End Up on Different Blockchainshttps://bitcoinmagazine.com/articles/how-bitcoin-unlimited-users-may-end-different-blockchains/Why Bitcoin Unlimited's "Emergent Consensus" Is a Gamblehttps://bitcoinmagazine.com/articles/why-bitcoin-unlimiteds-emergent-consensus-gamble/ via /r/Bitcoin http://bit.ly/2nhwrwM