The Canonical Transaction Chain (CTC) contract is an append-only log of transactions which must be applied to the OVM state. It defines the ordering of transactions by writing them to the CTC:batches instance of the Chain Storage Container. The CTC also allows any account to enqueue() an L2 transaction, which the Sequencer must eventually append to the rollup state.
The State Commitment Chain (SCC) contract contains a list of proposed state roots which Proposers assert to be a result of each transaction in the Canonical Transaction Chain (CTC). Elements here have a 1:1 correspondence with transactions in the CTC, and should be the unique state root calculated off-chain by applying the canonical transactions one by one.
Provides reusable storage in the form of a "Ring Buffer" data structure, which will overwrite storage slots that are no longer needed. There are three Chain Storage Containers deployed, two are controlled by the CTC, one by the SCC.