What is the main differences between ATX and Mini-ITX?

The main differences between ATX and Mini-ITX motherboards are their size and expansion capabilities. ATX motherboards are larger, typically measuring 305 x 244 mm, and offer more slots for RAM, PCIe cards, and additional features, making them suitable for high-performance builds. In contrast, Mini-ITX motherboards are smaller, measuring 170 x 170 mm, which limits the number of expansion slots and RAM capacity, but allows for more compact, space-saving builds. This makes Mini-ITX ideal for small form factor PCs, while ATX is better for more extensive setups.