LCR (local continuous replication)
this was mainly used for small business who wanted to replicate a copy of their Exchange database to another disk on the same server.
SCC (Single copy cluster)
was what I would call a traditional Exchange cluster which used shared storage to host the Exchange database.
CCR (cluster continuous replication)
was used to replicate Exchange database information between 2 Exchange server allowing for hardware and storage redundancy but was limited to 1 Active node and 1 Passive node.
SCR (standby continuous replication)
was introduced in Exchange 2007 SP1 to provide the ability to replicate Exchange databases to an disaster recovery location.
