Contracts, simply put, are restrictions on how tokens can be transferred, allowing users to specify the distribution of UTXOs through contracts. Many scaling solutions, such as the Lightning Network, are based on this principle, demonstrating that Bitcoin's scaling solutions heavily rely on introspection and contracts. In the crypto world, the most common method is commitment, often achieved through hashing. To prove that we meet the transfer requirements, a signature mechanism is needed for verification. Thus, contracts involve many adjustments related to hashing and signatures.