A seed phrase is a series of 12 or 24 words that acts as a recovery key for your cryptocurrency wallet. From this seed phrase, a key-pair is derived, which is used by signers to authorize and validate transactions. Essentially, the signer uses this key-pair to prove ownership of the wallet.
If someone obtains your seed phrase, they can generate the key-pair, effectively becoming the signer with full access to your cryptocurrency. Conversely, if you lose this phrase, you risk being unable to recover or access your funds. Thus, it’s crucial to store the seed phrase securely and privately.