The BIOS is the Basic Input/Output System. This is a chip which resides on the Motherboard within ROM (Read Only Memory) on older systems, or within some Flash memory on a more modern system. The BIOS is usually referred to as "firmware". It contains instructions which allow the motherboard to initialize the hardware components and perform the POST (Power On Self Test), before moving forward to the boot process and loading the main operating system such as Windows or Linux.
Boot sequence is the order in which a computer searches for nonvolatile data storage devices containing program code to load the operating system (OS). Typically, a Macintosh system uses ROM and Windows uses BIOS to start the boot sequence. Once the instructions are found, the CPU takes control and loads the OS into system memory.
The devices that are usually listed as boot order options in the BIOS settings are hard disks, optical drives, flash drives, etc. The user is able to change the boot sequence via the CMOS setup. Boot sequence is also called as boot order or BIOS boot order.
You may find the BIOS version on a Windows computer by running msinfo32 command at the command prompt. It will bring up the following window: