BIP39 means Bitcoin Improvement Proposal 39. The words are chosen from a certain list of 2048 typical English words that may be used to the crank out a binary seed (your private essential). Standard recovery phrases use a certain list of 2048 words following the BIP39 standard (Bitcoin Improvement Proposal https://throbsocial.com/story20788741/a-secret-weapon-for-bip39-words-to-numbers