An ITX motherboard is a Mini-ITX form factor motherboard. These motherboards are typically less than half the size of a standard ATX motherboard, and are designed to fit in small spaces such as an entertainment center or home server.
One of the main benefits of using an ITX motherboard is that they typically have fewer expansion slots than a standard ATX motherboard. This means that you will likely need to use an adapter to add additional components, such as a graphics card or hard drive.
Additionally, many ITX motherboards only have one RAM slot, which means that you will need to purchase an additional memory card if you want to install more than 1GB of RAM on your system.