When you press the power button, the CPU doesn’t immediately know how to read a game disc or display graphics. It looks to the BIOS for instructions. The BIOS performs a Power-On Self-Test (POST), initializes the hardware components, and loads the operating system kernel. On the PS2, this is what creates the iconic "towers" intro sequence and the system menu where you could browse memory cards or change settings.
The specific filename often found in emulation archives— scph10000.bin or variations including the date string—tells a precise story about the software version: Bios Japan V01 00 17 01 2000 Console 10000 Bin
