Bitcoin script is a programming language that is used to facilitate the creation and execution of transactions on the Bitcoin network. It is based on a stack-based, reverse-polish notation language and is used to create Bitcoin addresses and to validate transactions.
Bitcoin script is used to encode the conditions that must be met in order for a transaction to be considered valid. This includes the number of inputs and outputs, spending requirements, and the type of signature that must be included. Bitcoin script is also used to create smart contracts and multi-signature wallets.