Bitcoin Q&A: BCHABC vs. BCHSV Hard Forks

What happened with the Bitcoin Cash (BCH) hard fork on November 15th? What kind of fork was it? What is the difference between BCHABC / BAB and BCHSV / BSV (note: broad agreement on ticker symbols has not necessarily occurred yet)? What will OP_DATASIGVERIFY and Canonical Transaction Ordering (CTOR) do? Does the original chain still exist? Is there a hash war going on? What happens to coins from the prior BCH chain? What is replay protection?