Graphic card

VGA stands for Video Graphics Accelerator, serves to process data and graphics displayed on a monitor, VGA also has a processor called a GPU (Graphics Processing Unit) and requires memory as well.
Nowadays banayk motherboards on the market that use onboard VGA so you do not need to buy another VGA card, this is very helpful to save costs.
the difference between VGA OB (On Board) with a separate VGA with the motherboard are as follows:
OB-VGA does not have its own memory, so use some OB VGA RAM capacity that is in the computer for work, so it will make the performance of RAM to be slow, but now several manufacturers of motherboards has launched a motherboard with VGA OB and has its own memory.

OB-VGA has lower performance when compared to an external VGA, but if your computer is not too used to playing games, especially the latest 3D games that require a larger capacity VGA then you can still  VGA OB you have, now many motherboards with OB VGA that can match and even surpass the performance of an external VGA

OB-shaped smaller VGA to VGA external, it aims to save the cost of manufacture, small size is commonly called the microATX (mATX)