VGA Card function is to generate and output images to a display on the monitor. Now a days all motherboards have in-built VGA card. If it fails you have to add one VGA card on your mother board.
VGA card it stands for vedio Graphic Aray with our vga card any monitor or lcd will not display any thing mostly computers and have built in cards but if it stop working you can add new in other slot.
The functions of VGA card is for image render, and make good or best quality for our image, game, and video.
vga card function to process all the graphics to be displayed on the monitor. in the case of a game. VGA was the one who plays. sometimes a lot of misunderstanding that occurred, you should know that the processor and the ram is not much affect the performance of a game.
VGA ,vedio Graphics Aray with this system is enable to display any thing on your monitor or lcd and VGA occupy special space in RAM it is built in mother board.
some processor support onboard display and some don't. also, some motherboards have onboard display and some don't have. Apart from this, if somebody wants to have a better display then what is already inbuilt, they can go for a better vga.