The ASRock D1800B-ITX is a Mini-ITX motherboard that comes with a Celeron J1800 “Bay Trail-D” dual-core CPU soldered. It has one USB 3.0 and two SATA-300 ports, but its highlights are actually its low TDP and low cost, besides, of course, its small footprint.
The Celeron J1800 is an SoC (System on a Chip), meaning it has the CPU, GPU, memory controller, and chipset in the same chip. Even with all these components, the chip dissipates only 10 W. Despite its name, the Celeron J1800 is an Atom CPU targeted to desktop computers. It runs at 2.41 GHz (2.56 GHz boost clock) and has 1 MiB of L2 cache.
The Bay Trail-D family has also four-core processors, under the Celeron (Celeron J1850 and J1900) and Pentium (Pentium J2850 and Pentium J2900) brands, all of them with 10 W TDP, so you can find similar motherboards based on those quad-core processors too.
You can see the ASRock D1800B-ITX motherboard in Figure 1. It uses the Mini-ITX form factor, measuring 6.7” x 6.7” (170 x 170 mm).