A Secret Recovery Phrase (also known as a seed phrase or mnemonic) is a series of words generated by your cryptocurrency wallet that give you access to the crypto associated with that wallet.
The addresses/accounts in your wallet are mathematically derived from your Secret Recovery Phrase. Think of a wallet as similar to a house and its derived addresses/accounts as rooms. The Recovery Phrase would be the master key that opens all the rooms in that house, while a Private key only opens a specific room.
This is why it is so important to store it correctly and not share your Secret Recovery Phrase with anyone. As long as you have your seed phrase, you will have access to all the cryptocurrencies associated with the wallet that generated the phrase - even if you delete or lose the wallet. But if someone gets your Phrase, they will also have full access to your funds.
The words in the Secret Recovery Phrase belong to a specific list according to a standard, to know more you can read this article.
DO NOT share your Secret Recovery Phrase with anyone! If someone has access to your secret phrase, they will have access to your wallet. Phantom support will NEVER ask you for your secret phrase or your private key.