Do you want to put together a truly compact system while making as few concessions as possible in terms of performance? Then you quickly arrive at the mini ITX form factor. Although these motherboards are a niche, there is plenty of choice for those looking for a small board.
The ATX format is currently by far the favourite of hardware lovers. Although more and more components are integrated on the motherboard and processor, and therefore rarely many plug-in cards are needed, larger enclosures are apparently more suitable for beautiful - RGB-lit - showcases.
Anyone who looks more functionally at the PC phenomenon will soon realise that you usually build a system with one video card, two memory modules, and roughly one SSD and one hard disk. This leaves many connections on an ATX motherboard unused and, above all, a lot of space empty in an ATX housing.
Mini-ITX is an obvious alternative. This square form factor measures 17 by 17 centimetres and offers enough space inside for a modern PC. This is made possible by the high degree of integration mentioned above. The USB controller, PCI-e controller, network and audio, it's all on the PCB, either directly via the chipset or with a separate chip. Moreover, the processor provides the memory controller and even more PCI-e lanes, while a basic video card is often not included. This makes it perfectly possible to offer all the functionality you need on the small surface of an ITX board.
Don't you make any concessions at all? Of course you do: by definition you do not have the possibility to insert two video cards (because there is only room for one PCI-e slot), in terms of memory slots you are limited to two and there are usually fewer connection points for satellite storage. Moreover, the board is often a bit more complex with so much functionality on such a small surface, which increases the price: if you want to be small, you have to pay extra, in other words.
Keeping that in mind, an ITX system is still particularly interesting when you're looking for something powerful, but small. For example, in the living room, or because you're just small housed. If you often go to LAN parties, an ITX system is a lot easier to transport than a large ATX case, while the components are faster than what we find in an average gaming laptop. Anyway, a compact ITX gaming system is a lot less expensive than a high-end gaming laptop. Other applications for ITX are that you can use it as the basis of a home server, or as a second PC next to a larger 'main' system.