The Beacon Chain Ethereum 2.0 explainer you need to read first

"Ethereum’s Beacon Chain is the heart of a system where most content is too technical, niche, or not deep enough. Here, you’ll gain a gratifying understanding of the Beacon Chain’s elements and mechanics. Examples will explain key details at the right level to make you proficient and save time. We assume you have a solid foundation of Ethereum or Bitcoin, and some familiarity with Proof of Stake. Let’s dig into the bigger picture of shards, staking validators, attestations, committees, checkpoints, and finality."