BIP39 means Bitcoin Improvement Proposal 39. The words are selected from a selected list of 2048 frequent English words which may be used to the crank out a binary seed (your private vital). Should you be Uncertain about a selected word's spelling, use the research function (Ctrl+F on Windows/Command+F on https://socialicus.com/story4280606/how-much-you-need-to-expect-you-ll-pay-for-a-good-bip39-definition