A motherboard is the main printed circuit board (or PCB) in a computer system. It acts as the center for communication and the integral structure for the computer to operate. Which connects all of the other parts of the computer together as a unified system. A modern motherboard usually includes the following components:

• A CPU socket where the CPU is stored.
• DIMM Slots, or the so called RAM Slots is where RAM is installed.
• A Chipset is the set of integrated circuits that manages the data flow and communication between the CPU, memory, and peripherals.
• Expansion slots or PCIe, are slots where graphics cards are often installed. Storage connectors, are where storage devices ang installed.
• Power connectors are the sockets that receive power from the power supply.
• BIOS chips are where the firmware is used to initialize and test hardware before the operating system loads.
• Then the I/O ports are the connectors at the back that connect the different peripherals.

• The common ones are usually the consumer standards (ATX, Micro-ATX, Mini-ITX), are the industry's current standards. It is actively being sold, and nearly all of the PCs are composed of these mentioned motherboard types.
• The High-End or Specialized motherboards (Extended-ATX), is a larger variant of the ATX, usually meant for server builds.
• Another one is Legacy motherboards (AT Motherboard, LPX Motherboard, Mini-ATX), which are older and discontinued standards usually from the 1980s or 1990s that were the industry standards before.
• Last being the Failed/Niche Standards (BTX Motherboard, Pico BTX Motherboard), it is usually failed prototypes that failed to gain use for, or were too niche to be used in certain environments.

Form Factor	Build	CPU Slots	Memory Slots	Chipsets	BIOS	PCI Slots	SATA	Built-in Features
AT Motherboard	350 mm x 300 mm	1 (PGA/ZIF)	4-6 (SIMM/DIMM)	Intel i386/i486 era	Legacy BIOS	ISA/EISA, limited PCI	None (Used IDE)	Large size, I/O ports in the rear were non-standardized. (Obsolete)
ATX Motherboard	305 mm x 244 mm	1	2-4 (DIMM)	Modern (Intel Z/B/H, AMD X/B)	UEFI/BIOS	4-7 (PCIe/PCI)	4-10+	Current standard, Integrated I/O panel, better airflow.
BTX Motherboard	325 mm x 267 mm	1	2-4 (DIMM)	Intel 900 series (obsolete)	BIOS/UEFI	7 (PCIe/PCI)	4+	"Flipped" layout for optimized airflow (CPU exhaust), dedicated thermal module mount. (Obsolete)
Extended-ATX Motherboard	305 mm x 330 mm	1 (or 2 for server)	4-8 (DIMM)	High-End Modern (E.g. Intel Z-Series/AMD X-Series)	UEFI/BIOS	7-8 (PCIe)	8-12+	Maximum expansion, higher RAM capacity, best for multi-GPU/workstations.
LPX Motherboard	330 mm x 229 mm	1 (PGA/ZIF)	2-4 (SIMM/DIMM)	Older low-profile chipsets	Legacy BIOS	Riser Card only (2-3 slots total)	None (Used IDE)	Designed for slim cases; expansion cards run parallel to the board via a riser card. (Obsolete)
Micro-ATX Motherboard	244 mm x 244 mm	1	2-4 (DIMM)	Modern (Intel Z/B/H, AMD X/B)	UEFI/BIOS	2-4 (PCIe/PCI)	4-8+	Best balance of size, cost, and features, fits in smaller cases than ATX.
Mini ITX Motherboard	170 mm x 170 mm	1	2 (DIMM)	Modern (All current chipsets)	UEFI/BIOS	1 (PCIe x16)	4-6	Smallest size, ideal for compact (SFF) builds and HTPCs.
Mini-ATX Motherboard	284 mm x 208 mm	1 (PGA)	2-4 (DIMM)	Early Pentium-era chipsets	Legacy BIOS	4-6 (PCI/ISA)	Used IDE	A specific, slightly smaller early variant of the ATX standard (not the same as Mini-ITX). (Obsolete)
Pico-BTX Motherboard	203 mm x 267 mm	1 (LGA 775 era)	1-2 (DIMM)	BTX-era chipsets	BIOS/UEFI	1 (PCIe)	2-4	Ultra-compact version of the short-lived BTX standard. (Obsolete)