BIP39 means Bitcoin Improvement Proposal 39. The words are chosen from a specific list of 2048 popular English words which can be utilized to the create a binary seed (your personal important). Standard recovery phrases use a specific list of 2048 words following the BIP39 standard (Bitcoin Enhancement Proposal 39). https://atozbookmarkc.com/story19028501/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition