Canonical Chain

A canonical chain is the one with the most accumulated work. The accumulated work is the sum of difficulties of all the blocks in the chain.

Chain Reorganization

Chain Reorganization happens when CKB found a chain that has accumulated more work than the canonical chain. The reorganization reverts the blocks in the current canonical chain if needed, and switch the canonical chain to that better chain.

Live Cell

A cell is live if

it is found as an output in any transaction in the canonical chain, and
it is not found as an input in any transaction in the canonical chain.