BIP39 means Bitcoin Advancement Proposal 39. The words are picked from a certain list of 2048 typical English words that may be accustomed to the produce a binary seed (your private key). Standard recovery phrases use a selected list of 2048 words pursuing the BIP39 standard (Bitcoin Enhancement Proposal 39). https://pukkabookmarks.com/story18874545/bip39-phrase-generator-can-be-fun-for-anyone