How do Ledger Backups get stored? Scenario   

Say you have configured a ledger wallet with 10 BTC and 10 ETH. You then lose this said wallet but you have the 24 unique words. You buy another ledger wallet enter the 24 words and BAM, your wallet is back.

Question
My question is where did the backup come from ? And how is it encrypted.

Thanks!
Using words to back up wallets is a process described in BIP 39.

Basically, the mnemonic is converted into a seed. This seed is then used as the seed to a Heirarchical Deterministic (HD) wallet, as laid out in BIP 32. The seed is used to generate a Master Extended Private Key, from which all other private keys can be generated. The child key generation follows the standard of BIP 44 so it is compatible with other wallets too.

Thus, by backing up your mnemonic words, any time you enter them in a wallet, it can recreate the seed, then the master private key, then all your other keys, so your wallet is back.

References:


http://support.ledgerwallet.com/knowledge_base/topics/how-to-restore-my-backup-without-a-ledger-wallet