Consensus is the idea that a predetermined set of data on Computer A could be guaranteed to be the same—or consistent with—another predetermined set of data on Computer B.
Computer A would know its own directory structure and contents, as well as that of Computer B. To achieve consensus, changes on one computer would propagate to the other.
A cryptocurrency is an application of the blockchain; it is not a blockchain itself.
A distributed ledger is a database that is consensually shared and synchronized acrosås multiple sites, institutions, or geographies, accessible by multiple people. It allows transactions to have public "witnesses".
Most cryptocurrencies have third-party computers that validate transactions. They reward the validators with some cryptocurrency. In this way, a validator has a chance of taking a cut of a transaction.
This is a form of storing data.
Proof of Work
An earlier version of blockchain validation.
Proof of Stake
A version of validation which requires less energy consumption.
Third party computers used to validate cryptocurrency transactions, which minimizes the ability of users to defraud the system.