Bip39 Checksum. You should then do a standard recovery by using a command such as just one below. (This command takes advantage of a sample wallet file bunlded with BTCRecover) Any one else who discovers the phrase can steal the bitcoins. It has to be saved secret, one example is https://bookmarkvids.com/story20047293/bip39-wallets-https-linktr-ee-bip39-bip39-words-an-overview