Sharding
Sharding splits a blockchain’s data and workload into parallel pieces ("shards") so nodes only process a portion of the total.
In depth
Instead of every node validating every transaction, groups of nodes handle separate shards and the chain stitches their results together. It is a Layer 1 scaling approach borrowed from database design. Ethereum’s roadmap uses a form of data sharding to make rollups cheaper.
Why it matters
Sharding is one of the main answers to "how can blockchains ever handle global scale".