BIP39 stands for Bitcoin Advancement Proposal 39. The words are chosen from a certain list of 2048 common English words which may be accustomed to the create a binary seed (your non-public vital). Standard recovery phrases use a selected list of 2048 words pursuing the BIP39 standard (Bitcoin Enhancement Proposal https://socialbuzzfeed.com/story4963978/little-known-facts-about-bip39-words