Your motherboard is the foundation of your computer. It connects all the other components together, and without it your processor would be unable to process and your RAM unable to store memory. Motherboards also contain the core programming of your computer, known as the Basic Input/Output System (BIOS). You can access these during the boot-up process. In the BIOS, you'll be able to configure devices, boot order, fan speeds, and many other variables. ASUS motherboards include several unique features, as well, ranging from tweaking utilities to a "Turbo Key" that will automatically over-clock your system, giving it extra power at the cost of instability.
Start your computer. If it's already on, restart it.
Wait for your system to post. Posting is when white text appears on a black background.
Press the "Delete" key on your keyboard when your system states, "Press Del to enter setup." This will take you to your BIOS.