Primarily it refers to the size of a motherboard. It's actually about 80% (or so) the size of an ATX board. It should (the mobo) mount on the same bolt pattern as an ATX board, however, it won't cover all the holes.
When other products, (heat sinks, cases, power supplies and such), are mentioned in conjunction with Matx, it's generally to imply compatibility.
Intel lists Matx (motherboards) as about 9.60" x 9.60".
The ATX specs are 11.60" x 9.60".
With respect to cases a Matx only case would likely be called a "mini-tower".
Almost all "mid-tower" cases would accept both spec boards.
i dont think it always equates in less performance on lower end models less upgrade paths and such but on higher end models u get all the bells and whistles the real idea of micro-atx build is if you want something small and portable.
Yes I want something small and portableBUT
without compromising on performance
Will GTX 770 Graphics card
16 GB RAM (2 x 8GB)
Run equally well on a mATX motherboard? or will i get better results with an ATX mobo?