Most systems these days use the Unified Extensible Firmware Interface (UEFI). This is an interface between the hardware on a PC and the Operating System (OS). When the hardware begins, there is firmware that is loaded and starts initializing the hardware. Once the UEFI has initialized the hardware, it then loads the boot manager, and then loads the OS through the boot manager. Examples of Boot Managers are GRUB, rEFInd, Limine and others. The Boot Manager is the same as a Bootloader. There... https://www.linux.org/threads/linux-boot-management-with-efibootmgr.57749/