Sharding in blockchain is of two types — execution sharding and data sharding. There could be other types in the future, the crypto space evolves quickly.
In episode 41, what I explained was primarily execution sharding. Where the transaction execution is divided across several sub-chains for faster throughput.
However, Ethereum has moved away from the execution sharding roadmap and is now moving towards data sharding.
In data sharding, the validators form smaller subnets (shards) to verify and validate chunks of data posted by the rollups. Hence data sharding is a way to scale and improve data availability on Ethereum. Not every validator has to download all the data chunks, they only have to download and verify on a subnet level. Hence, data is sharded across several shards (logically).