Concurrency.
Multiple transactions making progress at the same time. On eUTxO, possible whenever the transactions don't touch the same UTxO.
Two separate supermarket checkout lanes serving customers at the same time because they're independent. eUTxO is full of independent lanes; only people fighting over the same box (UTxO) have to queue.
In depth
Concurrency on Cardano is granted by the UTxO model itself: two transactions that consume different UTxOs are independent and can be validated and ordered freely within the same block. Concurrency falls apart wherever many users want to read or update the same UTxO at once, that's contention, and it's why DEXes use batchers and oracles use reference inputs.
Example
Ten users each send ada from their own wallets to ten different recipients, all ten transactions are concurrent. Ten users trying to swap against the same DEX pool UTxO are not.