Secure Boot is a feature of the Unified Extensible Firmware Interface (UEFI) that protects the boot process and prevents unauthorized software and malware from loading during the system startup. When enabled, Secure Boot checks the signatures of boot applications, including bootloaders and operating systems, against a database of trusted signatures. If an unsigned or untrusted application is detected, the system will not boot, thereby enhancing the device's security against attacks like bootkits and rootkits.