A series of words that can be used to recover a person’s crypto wallet.
The Long Explanation
Also known as a secret recovery phrase, this is a series of words, usually ranging between 12 and 24, that can be used by a person to recover their crypto wallet in case they lose access to their wallet or forget its password.
Your seed phrase will be generated by the crypto wallet (ie. Metamask)when you first create one, and this is one piece of information that has to be written down on paper and stored safely.

If you happen to lose access to your crypto wallet for some reason, the seed phrase can be used to download the wallet on a different device and gain access to your cryptos. Since anybody with the seed phrase can access your wallet, it is highly recommended to refrain from storing it on the internet and not share it with anyone else.