Blockchain rollups are a layer 2 scaling solution designed to increase the throughput of transactions on a blockchain network. They work by bundling multiple transactions into a single batch, which is then processed on the main chain. This approach significantly reduces the load on the base layer, allowing for faster and cheaper transactions. There are two main types of rollups: optimistic and zk-rollups. Optimistic rollups assume transactions are valid by default and only check for fraud when challenged, while zk-rollups use cryptographic proofs to validate transactions off-chain before submitting them to the main chain.