ETH2 is where Ethereum goes from Proof of Work to Proof of Stake and as a result uses 99% less electricity.
The second phase of ETH2 is sharding where instead of Ethereum being one big chain it has one execution chain and 64 additional data shards. This makes it scale incredibly well when it's a settlement layer for rollups (up to 14 million TPS with 1024 shards - See https://polynya.medium.com/conjecture-how-far-can-rollups-da...)
Yes and the point there isn't so much that on-chain transactions are "supposed to be expensive," but that zkrollups are just as secure as on-chain transactions but scale an order of magnitude better than executable shards, so executable shards start to look a little superfluous.
The researchers have floated the possibility of incorporating zkrollup tech into L1 eventually, but with the tech advancing so quickly it's hard to say whether it will ultimately make sense.
The researchers have floated the possibility of incorporating zkrollup tech into L1 eventually, but with the tech advancing so quickly it's hard to say whether it will ultimately make sense.