The seed phrase is your master "password". Every wallet/address has a master password (or seed phrase). Even the wallet/address assigned to you by a CEX like Coinbase has a seed phrase (but they keep custody of it, not you). Seed phrases are composed of 12 (or 18 or 24) words from the BIP39 Standard and are just a translation of the random character string that cryptos actually use.
https://cryptonews.com/academy/seed-phrase/
When you get a Ledger and set it up, you will generate a master password/seed phrase. You should safeguard this password. I got the Cryptotag Zeus from Ledger to punch the code into titanium plates. No worries about fading ink, water or fire or so on. With your seed phrase secured, you can gain access to your wallets/addresses on any Ledger device - so if your Ledger Nano/Flex shits the bed, you can replace it and recover access to your wallets/accounts.
Ledger introduced a "Ledger Recover" service that is provided by CoinCover. Reading through their service agreement, it sounds a lot like its structured similar to what Unchained Capital or a multisig wallet does:
https://www.coincover.com/ledger-recover-terms-and-conditions
It is not a back door into the Ledger device. It's an optional service that distributes safeguarding of your seed phrase.