A seed phrase in Bitcoin is a series of 12 or 24 words generated from a set of 2048 words that serves as a backup for accessing a Bitcoin wallet. This phrase can be used to regenerate the wallet's private key, allowing the user to recover their Bitcoin if they lose access to the wallet. The 24-word seed phrase provides an extraordinarily high level of security, as it creates an enormous number of possible combinations—more than the number of atoms in the universe.

This vast number of potential combinations makes it practically impossible for anyone to guess or brute-force the seed phrase, ensuring the security of the Bitcoin associated with it.