BitLocker is a security feature that came with Windows Vista; it encrypts your hard drive. The intention is to protect the data from being stolen or falling into the wrong hands. The key to unlock the encrypted drive is well-protected by a Trusted Platform Module (TPM) that Windows owns and controls.
TPM is a cryptographic, tamper-resistant module. It stores biometric data, such as the new Windows Hello feature that allows you to sign in to Windows by using face or fingerprint. All these features are built in to Windows.
Regarding BitLocker, the 48-digit recovery key is securely placed in Active Directory attached to the Computer object, so it's easy to recognize.