When you own cryptocurrencies, what you really own are “private keys”. They are a unique and critical piece of information which is used to sign your cryptocurrency transactions and move your funds to a new address. Whoever has access to this data can have access to your assets.
These private keys are safeguarded inside the secure chips of Ledger hardware wallets, but they also exist as a physical backup on the form of 24 words. It is called a “recovery phrase” and is used to reinject the private keys in a new device in case of loss or destruction of your hardware wallet. Note that the “private keys” and the “recovery phrase” are exactly the same information: only the representation is different - binary in one case, human readable words in the other.
The need to shield your backup
Your Ledger hardware wallet is safeguarding your private keys, but anything can happen to the device (destruction, theft, malfunction…) and therefore you always need to keep a backup for emergency recovery. While you daily use it, you do not have to remember or type this recovery phrase, the Ledger device stores it for you, you simply have to enter your PIN code. But your recovery phrase is your backup, the indispensable way to recover your wallets, your accounts, your funds, in case of loss of your device. So it is definitely essential to have a safe and - as far as possible - indestructible backup of this seed. Let's imagine your device has been theft, and / or your 24 words have been erased, burnt, thrown away by mistake. Your funds could be lost forever.