What is Trustless?
“Trustless” is a term associated with Distributed Ledger Technology (DLT) such as blockchain-based networks because participants involved do not need the support and systems of a "trusted" central party, such as a bank, broker, lawyer or other centralized authority to facilitate the validation, execution and journaling of transactions between multiple parties. Instead, those parties rely on DLT and its algorithms to take the place of a central party. Recognizing the absence of a central trusted party, public distributed ledgers are often said to be trustless.
This does not mean that a DLT is an insecure free-for-all that’s not to be trusted. Rather, it means that instead of relying upon a central, “trusted” authority such as a bank to verify the accuracy and integrity of transactional behavior, a distributed ledger is typically made up of multiple distributed computers that work together across a peer-to-peer network to algorithmically ensure the security, order and accuracy of the ledger. This work is conducted in a decentralized, automated manner that’s coordinated among the ledger’s computers according to conventions and mathematical principles of distributed computing that are specific to each DLT network, of which Bitcoin is one, but there are many others.
To facilitate this trustlessness, DLTs rely on consensus algorithms so that the transacting parties can algorithmically reach an agreement or a consensus on a single truth without needing to know or trust each other.