BIP39 means Bitcoin Advancement Proposal 39. The words are picked from a particular list of 2048 widespread English words which may be accustomed to the crank out a binary seed (your personal critical). This text explains BIP39, the standard that defines how seed phrases are made, and summarizes how BIP32 https://zenwriting.net/keenanctdp/h1-b-unlocking-the-power-of-bip39-a-comprehensive-look-at-word-lists-and