What is wallet?

Software or hardware that stores the keys controlling your crypto and lets you send and receive it.

The name is the single most misleading word in the subject. A wallet holds no coins. Coins are entries on a blockchain, and they never leave it. What a wallet holds is the private key that can authorize changing those entries, which is why losing a wallet loses the coins and why anyone who copies your keys owns them too.

Once that is clear, most of the rest follows. Backing up a wallet means backing up the key material, not the app. Moving to a new phone means restoring the keys, not transferring a balance.

How it works

Nearly all modern wallets are hierarchical deterministic, meaning every key is derived mathematically from one master secret. That secret is presented to you as a seed phrase, commonly twelve or twenty-four words drawn from a fixed list defined in BIP-39, with the derivation structure defined in BIP-32 and BIP-44. Any compliant wallet can reconstruct the same accounts from the same phrase, which is why the phrase is the backup and the application is interchangeable.

Wallets divide along two axes. The first is who holds the keys. A custodial wallet, which is what an exchange account is, means a company holds them and you hold a claim. A self-custody wallet means you hold them and nobody can freeze, restore, or reverse anything.

The second is whether the key ever touches an internet-connected device. A hot wallet keeps keys on a phone or browser, which is convenient and exposed. A cold wallet or hardware wallet keeps them on a device that signs transactions internally and never reveals the key, which is inconvenient and far harder to attack remotely.

Neither axis makes a wallet good or bad. They describe which failures are possible.

Example

Illustrative. You buy 0.05 BTC on an exchange. That balance is a database row, and the exchange holds the keys.

You withdraw to a hardware wallet whose seed phrase you wrote on paper and stored offline. The coins now sit at an address only your key can spend. If the exchange fails tomorrow, your holding is unaffected. If your house burns down and the paper with it, the coins are unrecoverable by anyone, including you, because there is no support line for a key that no longer exists. The same act removed one risk and introduced another.

Why it matters when you buy

Where the coins end up is a decision you make at purchase time, and it changes what can go wrong. Exchange custody means the platform's solvency and security are yours. Self-custody means your backup discipline is. The guide on self-custody versus exchange custody sets out the tradeoff, and the guide on your first crypto wallet covers setup.

Related terms

• private key: what a wallet actually stores
• seed phrase: the backup every key derives from
• hot wallet: keys on a connected device
• cold wallet: keys kept offline
• custodial: someone else holding the keys
• self custody: holding them yourself

Questions

Do my coins live inside the wallet app?

No. They are recorded on the blockchain, and the app holds the keys that authorize spending them. Deleting the app changes nothing as long as you have the seed phrase.

Can I use one wallet for every coin?

Many wallets support several chains, and not all of them, and each chain uses its own address format. Sending an asset to an address on the wrong network is the most common way people lose funds this way.

Is a hardware wallet necessary?

It depends on the amount and how you use it. A hot wallet is reasonable for small balances you transact with, and a hardware wallet reduces remote attack risk for holdings you rarely move.