Rollups are a type of scaling solution used in blockchain technology to improve transaction speed and reduce costs. They work by bundling multiple transactions into a single batch, which is then processed on the main blockchain. This helps to alleviate congestion and allows for more efficient use of network resources. There are two main types of rollups: Optimistic Rollups and ZK-Rollups. Optimistic Rollups assume transactions are valid and only check them if challenged, while ZK-Rollups use cryptographic proofs to verify transactions instantly. Both methods aim to enhance the performance of blockchains like Ethereum without sacrificing security.