In BFT consensus algorithms, Validators must come to agreement before adding any blocks to the chain. The name comes from the "Byzantine generals problem", a thought experiment that dealt with how a group of military generals, who could not communicate directly with each other, could come to a decision about whether to attack or flee. This issue doesn't just deal with the case of the general being a malicious actor, but also the case of the messenger being the one who changed the vote, or simply not being able to deliver the message. In a computer system, Byzantine faults are used to describe errors that can occur from an actor either being compromised or faulty. These types of consensus mechanisms, while useful for blockchain consensus, were originally developed to enable aircraft to rely upon their sensor data to make software decisions as long as a certain threshold of their sensors were always in agreement.