The boot process is the sequence a computer follows when it starts up and loads its initial software state. It begins with firmware such as BIOS or UEFI, which checks hardware, applies basic settings, and hands control to a bootloader. The bootloader then loads the operating system kernel and enough supporting code to bring the system into a usable state. What appears on screen first, whether a logo, a login prompt, or a command shell, is part of that startup path.
In cyber security, the boot process matters because it is one of the earliest trusted execution paths on a device. If an attacker can modify firmware, a bootloader, or startup configuration, they may gain persistent access that survives reboots and is harder to detect. Defenses such as Secure Boot, signed boot components, measured boot, and trusted disk encryption aim to protect this early stage and ensure the machine starts from a known-good state.