Blockchain is part of a suite of DLTs that can be programmed to record and track anything of value. Blockchain is essentially a shared database filled with entries that must be confirmed (verified) and encrypted. Blockchain is built around cryptography, and cryptography enables the sharing of information in the presence of adversaries.
If we have consensus as a sailing crew, then we all agree on the route we will take, so consensus is agreement and mutual approval. The blockchain establishes an agreement between all the participants in the network to determine who in the network is allowed to append a block to the chain.