Script

A script is recorded on the blockchain with each transaction instructing the receiver of funds on the steps required to access them.

For Bitcoin, the two basic steps a receiver takes:

1. Providing their public key identifying the destination address
2. A signature demonstrating control of the private key corresponding to the public key provided

Scripts can be enhanced to require additional steps before funds are released. For example multi-sig being incorporated into a script requires 2 or more private keys be provided before accessing the funds.

The sender defines the parameters for the receiver to access the funds in the script using opcodes. Opcodes are the pre-defined instructions supported by blockchains defining how transactions can be conducted across the network.

Transactions on the blockchain are not finalized until all of the steps in the script are successfully completed and verified.

Further Reading Script

Time Locked Bitcoin Transactions