Pre-boot authentication
Pre-Boot Authentication (PBA) serves as an extension of the BIOS or boot firmware and guarantees a secure, tamper-proof environment external to the operating system as a trusted authentication layer. The PBA prevents Windows or any other operating system from loading until the user has confirmed he/she has the correct password or other credentials.[1]
Pre-Boot Authentication since a basic OS is still loaded prior to the main operating system. However, the term is most often used to describe a fully loaded OS used for authentication instead of a BIOS password, which is still technically "Pre-Boot".
Pre-Boot Authentication is generally provided by a variety of Full Disk Encryption vendors, but can be installed seperately. Some FDE solutions can function without Pre-Boot Authentication, such as Hardware-based Full Disk Encryption. However, without some form of authentication, encryption does not provide any form of data protection.