Important Key Terminology to understand high availability or site resilience in Exchange Server

Important Key Terminology to understand high availability or site resilience in Exchange Server
Active Manager	An internal Exchange component which runs inside the Microsoft Exchange Replication service that's responsible for failure monitoring and corrective action through failover within a database availability group (DAG).
AutoDatabaseMountDial	A property setting of a Mailbox server that determines whether a passive database copy will automatically mount as the new active copy, based on the number of log files missing by the copy being mounted.
Continuous replication - block mode	In block mode, as each update is written to the active database copy's active log buffer, it's also shipped to a log buffer on each of the passive mailbox copies in block mode. When the log buffer is full, each database copy builds, inspects, and creates the next log file in the generation sequence.
Continuous replication - file mode	In file mode, closed transaction log files are pushed from the active database copy to one or more passive database copies.
Database availability group	A group of up to 16 Exchange 2016 servers that hosts a set of replicated databases.
Database mobility	The ability of an Exchange 2016 mailbox database to be replicated to and mounted on other Exchange 2016 servers.
Datacenter	Typically this refers to an Active Directory site; however, it can also refer to a physical site. In the context of this documentation, datacenter equals Active Directory site.
Datacenter Activation Coordination mode	A property of the DAG setting that, when enabled, forces the Microsoft Exchange Replication service to acquire permission to mount databases at startup.
Disaster recovery	Any process used to manually recover from a failure. This can be a failure that affects a single item, or it can be a failure that affects an entire physical location.
Exchange third-party replication API	An Exchange-provided API that enables use of third-party synchronous replication for a DAG instead of continuous replication.
High availability	A solution that provides service availability, data availability, and automatic recovery from failures that affect the service or data (such as a network, storage, or server failure).
Incremental deployment	The ability to deploy high availability and site resilience after Exchange 2016 is installed.
Lagged mailbox database copy	A passive mailbox database copy that has a log replay lag time greater than zero.
Mailbox database copy	A mailbox database (.edb file and logs), which is either active or passive.
Mailbox resiliency	The name of a unified high availability and site resilience solution in Exchange 2016.
Managed availability	A set of internal processes made up of probes, monitors, and responders that incorporate monitoring and high availability across all server roles and all protocols.
*over (pronounced "star over")	Short for switchovers and failovers. A switchover is a manual activation of one or more database copies. A failover is an automatic activation of one or more database copies after a failure.
Safety Net	Formerly known as transport dumpster, this is a feature of the transport service that stores a copy of all messages for X days. The default setting is 2 days.
Shadow redundancy	A transport server feature that provides redundancy for messages for the entire time they're in transit.
Site resilience	A configuration that extends the messaging infrastructure to multiple Active Directory sites to provide operational continuity for the messaging system in the event of a failure affecting one of the sites.