Term
Private key
A private key is the secret cryptographic number that authorizes spending from a specific cryptocurrency address — anyone who has the private key controls the funds at that address, so it must never be exposed to a networked device.
Every cryptocurrency address is derived mathematically from a private key. The private key is typically a 256-bit random number; from it, the wallet software derives a public key, and from the public key it derives the on-chain address. The one-way math means the address is safe to share, but if the private key leaks, whoever has it can sign transactions from the address and move the funds.
A wallet is essentially a program that manages one or more private keys and constructs signed transactions with them. A "seed phrase" is a compact encoding of a master private key, from which every individual per-address key is derived. A "hardware wallet" is a device that holds private keys inside a secure element and signs transactions on-device so the key never touches a networked computer.
The single most important rule: the private key (or seed phrase encoding it) must never be entered into a website, sent in a message, stored in cloud drive, screenshotted, or shared with anyone claiming to be "support." Every legitimate crypto operation the wallet does uses the key locally — it is never uploaded, revealed, or "verified" by any external service.
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