Currently the Ethereum blockchain is all housed on one chain. Over time this has gotten very long and takes a lot of storage space. In Eth2, there will be shard chains which are smaller chains that run alongside each other to reduce the total space required for each chain. Additionally, there will be more transactions that can take place simultaneously because there are multiple active chains. The Beacon Chain will act as the controller for the various shard chains. The Beacon Chain will allow stakers to validate their shard chains as well as propose new shard blocks.
Learn about the functions of the Beacon Chain and its Shard Chains
Understand how Rollups will improve the speed and scalability of the Ethereum network