Smart transactions enable smart contracts

Blockchain ledger technology opens the door not only to decentralized transactions, but also to smart (that is, automated and computable) transactions and smart (computable and self-executing) contracts that can take advantage of smart transactions. A smart contract is a digitally signed, computable agreement between two or more parties. A virtual third party—a software agent—can execute and enforce at least some of the terms of such agreements.

Source: Blockchain Introduction and Forecast: PwC