Task to create a Replication Glossary / Dictionary of Terms in Wiki:

Examples of terms to define:

Replication - Concept of keeping multiple copies of your data
Availability - Concept in event server goes down, still access data 
“Durable Replica Set” - Failover can take place quick, no seconds will be lost (as if nothing has happened) 
Standalone Node - System with 1 server only 
Replica Set - Group of nodes (mongod) with copies of same dat. Primary node handles primary interaction and secondary sync via asych mechanism 
Failover - When primary nodes goes down, a secondary node takes over as primary 
Election - When secondary nodes elect which node will be the primary node in a failover 
rolling upgrade: start the secondaries first, bring them back up, step down primary, then update primary to maintain availability 
Sync source: who are you syncing from. The primary or secondary (in chaining)
Raft:
Arbiters / P-S-A: Node that holds no data, vote in election, cannot be primary
Write Concern: 
Read Concern:
enableMajorityReadConcern (eMRC=false) :
Planned Elections:
Unplanned Elections:
Priority Takeover:
Catchup Takeover:
OpLog:
Heartbeats:
Initial Sync:
Rollbacks:
Transactions:
Retryable writes: