BIP39 means Bitcoin Enhancement Proposal 39. The words are picked from a particular list of 2048 frequent English words that may be accustomed to the produce a binary seed (your personal important). Standard recovery phrases use a certain list of 2048 words pursuing the BIP39 standard (Bitcoin Improvement Proposal 39). https://guidemysocial.com/story4188874/the-greatest-guide-to-seed-phrase-bip39