Consensus vs Policy

What is the difference between consensus and policy checks? Both seem to be related to validating transactions. We can learn a lot about the answer to this question from sdaftuar’s StackExchange answer.

The answer teaches us that policy checks are a superset of validation checks —  that is to say that a transaction that passes policy checks has implicitly passed consensus checks too. Nodes perform policy-level checks on all transactions they learn about before adding them to their local mempool. Many of the policy checks contained in policy are called from inside validation, in the context of adding a new transaction to the mempool.