Press "receive" twice in a row on the same wallet, and two different addresses will appear. Every beginner sees this as a defect, and some even reinstall the app thinking they've lost the first one. They haven't. The wallet is doing what it's supposed to, and understanding why changes the way you use Bitcoin forever.
An address is not an account. A bank account is a registration: it exists within a bank, has your name, lasts for decades, and is singular. An address is a destination, calculated from one of the keys generated by the seed from the previous lesson. The wallet has billions of them available and provides the next unused one each time you request it. None need to be created beforehand, and they never run out.
There is also no one issuing them. No one approves an address, no institution registers it, and the network doesn't know it exists until the day someone sends a payment to it. You can generate thousands of addresses per second on a computer that has never seen the internet, inside a closed room. It's the exact opposite of opening an account.
The formats have changed over time, and they all coexist. The old ones start with 1. Those starting with 3 appeared for contracts and later for the first version of SegWit. Addresses starting with bc1q are the 2017 format, written only in lowercase, and those starting with bc1p, from 2021, are for Taproot. Paying from one format to another always works; the difference appears in the transaction size and, with it, the fee in the next lesson.
Typing incorrectly doesn't send money into the void, and this is intentional. The old format already excluded confusing characters — zero and the letter O, uppercase I and lowercase l — and every address carries a checksum at the end. A swapped letter produces a sequence that doesn't add up, and the wallet rejects it before sending.
The costly mistake is another, and it's not yours. Addresses are copied and pasted, and there are viruses that monitor the clipboard: the moment a Bitcoin address appears there, it swaps it with the attacker's address. In 2017, Kaspersky described one of these, the CryptoShuffler, which had collected the equivalent of about $150,000 just by doing this, without ever touching any wallet. The defense is tedious but effective: after pasting, check the first and last characters with what the recipient sent. Dedicated devices exist largely because of this — they display the address on their own small screen, which the computer virus cannot control.
The part almost no one mentions is the history. Everything that enters and exits an address remains public forever, and anyone can check it in ten seconds. In June 2011, WikiLeaks published an address to receive Bitcoin donations; it remains there, and the entire world can see every donation it has received since then, with date and amount. For a public campaign, this is great.
For you, it's terrible. If a single address receives your salary, the sale of your bicycle, and a payment from a friend, all three things are linked at the same point — and the friend who paid once can see how much you earn and how much you have. A new address for each receipt is not paranoia; it's the only way not to publish your own statement. The wallet does this automatically, for free, if you let it. What the blockchain reveals about its users, and what can be done about it, is covered in an entire lesson in the intermediate track.
A used address doesn't stop working, and it's good that it doesn't. A late payment sent to an address from two years ago lands in your wallet just the same, because its key came from the same seed as all the others. Reusing is bad for what it reveals, not because it breaks.
The other half of the conversation is missing: what happens on the payer's side. In the next lesson, your first transaction — the fee, the wait, and the change you didn't ask for.