ZK rollups/EVMs are one among the myriad of arguably badly named things in maths & CS. They are named so because they are an implementation of what is called Z

ZK rollups/EVMs are one among the myriad of arguably badly named things in maths & CS. They are named so because they are an implementation of what is called ZK proofs, but they leverage them to be able to prove a succession of modifications of the state (i.e. the accounts and their money) in a quick & easy way to check. As a simplification, you may think of them as a hash of transactions & smart contract executions that are a tad expensive to compute, but trivial to check. The end goal typically being to multiplex multiple level-2 transactions onto a single Ethereum transaction to enhance bandwidth and reduce fees. However, they are not ZK in the applied sense of it; e.g. they do not even try to mask the operations; anyone could rebuild them themselves with a bit of effort.