BIP39 means Bitcoin Advancement Proposal 39. The words are selected from a selected list of 2048 typical English words which may be accustomed to the produce a binary seed (your non-public important). Standard recovery phrases use a certain list of 2048 words following the BIP39 standard (Bitcoin Improvement Proposal 39). https://bookmarkextent.com/story20471817/phrases-with-bit-an-overview