A recovery phrase is a list of ordinary words, usually 12 or 24, that a crypto wallet shows its user when the wallet is created. Typing the words into compatible wallet software recreates the wallet's keys and gives full control of its funds. "Recovery phrase" is simply another name for a seed phrase, where the full explanation is.
Most wallets follow the Bitcoin Improvement Proposal known as BIP-39, which picks the words from a fixed list of 2,048. The phrase encodes the master secret from which every private key in the wallet is derived, so anyone who sees it can take the funds. That is why users of a non-custodial wallet or a hardware wallet are told to write it down offline and never type it into a website or share it with "support" staff.