What are the features of motherboard.

The ones that matter most to PC builders and upgraders are ATX, MicroATX, and Mini-ITX. ATX is sometimes referred to as "standard ATX," and ATX boards (usually, but not exclusively) measure 9.6x12 inches. They're what you'll see in most midtower or larger PC cases-what most of us think of as traditional tower PCs. A few multi-CPU boards, intended for servers and workstations, and some outliers (such as EVGA's Classified series boards) support larger ATX "standards" such as Extended ATX and XL-ATX, but these won't be of interest to most PC upgraders or builders. The key thing to know apart from the size factor: ATX boards will have more expansion slots than MicroATX or Mini-ITX ones.