Both are secret information that you should keep securely because it gives you exclusive access to a specific space inside the blockchain. With these secret keys, you can interact with the blockchain space and move it around, change its size and form. Is there any difference between the two? Yes. A private key is a big random number represented in alphanumeric format. It is used to derive a corresponding public key and a specific address, which you will see in your wallet when clicking the "receive" button. The private key to the given address will be used to send funds to another address. A seed phrase, on the other hand, is a big random number represented as a set of several English words. The software you are using can take this big random number and generate millions of millions of millions of private keys that may be later used to generate millions of millions of millions of addresses which you can use to receive your coins. Each seed phrase always generates the same set of private keys, so you don't need to write them down. Just make sure that you keep your seed in a secure offline place no one unwanted knows about.