BIP39 stands for Bitcoin Enhancement Proposal 39. The words are chosen from a particular list of 2048 popular English words that may be used to the produce a binary seed (your private key). Standard recovery phrases use a particular list of 2048 words following the BIP39 standard (Bitcoin Advancement Proposal https://bookmarkeasier.com/story19329583/5-simple-techniques-for-bip39-word-list-pdf