Five short steps, written in plain words and checked against xrpl.org.
Step 1
What is a blockchain?
A blockchain is a shared record book that many computers keep at the same time, so no single person controls it.
Each new page is linked to the one before it. On many blockchains that page is called a block. On the XRP Ledger it is called a ledger version. The chain of pages is what people mean by a blockchain. Everyone who keeps a copy can check that the book still matches.
Step 2
Why share the book?
If only one person held the notebook, they could quietly change a page. When many computers hold the same copy, a secret change would not match the others, and it would get rejected.
To add something new, the computers have to agree it is correct.
Step 3
That agreement is called consensus.
Consensus is the process of agreeing on the next page of the book: which new entries to add, and in what order.
Some blockchains reach consensus through mining, which uses a lot of energy. The XRP Ledger takes a different path.
Step 4
How the XRP Ledger reaches consensus
On the XRP Ledger, servers called validators compare notes and agree on the next ledger. They share lists of new transactions, update their proposals, and keep going until a supermajority agrees. Anyone can run a validator.
A new ledger usually closes every few seconds, typically about 3 to 5 seconds. There is no mining. Transaction costs are tiny, and the XRP Ledger has been running since June 2012.
These details match xrpl.org, including the ledger close time and the launch year.
Step 5
A few simple XRPL basics
Once you know how agreement works, three everyday words show up again and again: accounts, XRP, and transactions.
Accounts
An account on the XRP Ledger is a holder of XRP and a sender of transactions. It is identified by an address, and it keeps a sequence number so each transaction is applied in the right order and only once.
To exist on the ledger, an account must hold a small amount of XRP in reserve. That helps keep the shared book from filling up with empty or leftover accounts. The current base reserve on Mainnet is 1 XRP.
XRP, the native asset
XRP is built into the XRP Ledger. It is not a separate token added later. Accounts can send XRP directly to one another, and a tiny amount of XRP is used to pay the cost of a transaction.
Transactions
A transaction is a signed instruction that asks the ledger to change something, such as sending XRP from one account to another.
Every transaction must destroy a small amount of XRP as a transaction cost. That XRP is not paid to anyone; it vanishes. The usual minimum for a standard transaction is 10 drops. One drop is one millionth of one XRP. The cost can rise if the network is busy, which helps protect the ledger from junk.