The following links are placeholders for further research and learning.

TermShort DefinitionLink
CAP TheoremTradeoff between Consistency, Availability, and Partition ToleranceCAP Theorem
ConsensusAgreement among distributed nodes on a single value or sequenceConsensus Algorithms
PaxosA family of protocols for consensus under crash failurePaxos
RaftReadable consensus algorithm used in many systemsRaft
QuorumMinimum number of nodes agreeing for a decisionQuorums
Vector ClockData structure tracking causality among eventsVector Clocks
Gossip ProtocolPeer-to-peer state dissemination protocolGossip Protocols
2PCProtocol for distributed transactions with a coordinatorTwo-Phase Commit (2PC)
3PCNon-blocking extension of 2PCThree-Phase Commit (3PC)
SagaPattern for breaking long transactions into local + compensating actionsSaga Pattern
Leader ElectionProtocol to dynamically choose a coordinatorLeader Election
Eventual ConsistencyGuarantees all replicas converge eventuallyEventual Consistency
State Machine ReplicationReplicating deterministic services across nodesState Machine Replication
Partial FailureSome components fail while others operate correctlyPartial Failure
Split-BrainCluster splits and both sides believe they’re the leaderSplit-Brain Scenarios
Network PartitionLoss of communication between parts of the systemNetwork Partition
Fault ToleranceSystem continues to operate under failureFault Tolerance
Distributed LockMechanism to ensure exclusive access to resourcesDistributed Locking
HeartbeatPeriodic message used to detect node livenessFailure Detectors
IdempotencyOperation can be repeated safelyIdempotency