I would stick to the central elements of blockchain-based cryptocurrency. Those take long enough to grok on their own.

ie. the idea of a public ledger which everyone keeps a copy of. New pages are added by a process of consensus. That process of consensus always builds upon the prior pages. They have a game-theory based mechanism to discourage cheating, where even when cheating is allowed within the cryptographic rules, cheaters always incur a high risk of loss. Generally blocks created by cheaters are not built upon, and the cost to create the block is a loss for the cheater.

Proof of work as the original consensus algorithm should certainly be discussed although many modern blockchains use alternatives such as Delegated Proof of Stake on Steem.