BIP39 means Bitcoin Improvement Proposal 39. The words are chosen from a certain list of 2048 widespread English words which can be accustomed to the produce a binary seed (your private critical). Safety: Any one with your seed phrase can Management your resources. Secure it securely and avoid sharing it. https://allkindsofsocial.com/story4353510/new-step-by-step-map-for-ledger-seed-phrase-bip39