As described in this article, the BIP39 standard describes how a seed phrase is constructed. Related to BIP39, the most prominent wallet standards include BIP32 and BIP44: BIP32 ("Hierarchical deterministic wallets") lays out a framework for Hierarchical Deterministic wallets (HD Wallets) for Bitcoin so that the wallet software can control multiple separate Bitcoin accounts using a single seed phrase. Furthermore, BIP44 ("Multi-account hierarchy for deterministic wallets") defines the same organizational hierarchy for managing multiple accounts in deterministic wallets for all other than Bitcoin cryptocurrencies, like Ethereum, Dogecoin, etc. BIP32 and BIP44 work together to add flexibility, privacy, and interoperability to HD Wallets. HD Wallets extend the capabilities of deterministic wallets, allowing for the management of a huge number of keys, all of which are derived from the original BIP39 mnemonic sentence (seed phrase). For the purposes of the guides on our website, we will focus on how to manage the BIP39 seed phrases, since it is supported by every modern crypto wallet, and it is the core thing to understand and be able to properly backup almost any crypto assets. However, you may come across wallets like Coinomi which also use BIP44 and default to 24-word seed phrases. Feel free to learn more about all of the BIP cryptocurrency standards that may be relevant to you!