Abbreviations use generally always cause misunderstanding in communication. Below are some commonly use Graphic Array terminology now explains to make you wiser.

• VGA, or "640 x 480" with 16 colours or “320 x 200” with 256 colours.
• SVGA, or "800 x 600" - This is a very popular resolution today, because of its attractive prices and great images. 
• XGA, or "1,024 x 768" - XGA are generally more expensive, and are an equally popular resolution format to SVGA.

VGA 

Abbreviation of video graphics array, a graphics display system for PCs developed by IBM. VGA has become one of the de facto standards for PCs. In text mode, VGA systems provide a resolution of 720 by 400 pixels. In graphics mode, the resolution is either 640 by 480 (with 16 colors) or 320 by 200 (with 256 colors). The total palette of colors is 262,144.

Unlike earlier graphics standards for PCs -- MDA, CGA, and EGA -- VGA uses analog signals rather than digital signals. Consequently, a monitor designed for one of the older standards will not be able to use VGA.

Since its introduction in 1987, several other standards have been developed that offer greater resolution and more colors, but VGA remains the lowest common denominator. All PCs made today support VGA, and possibly some other more advanced standard.

SVGA 

Short for Super VGA, a set of graphics standards designed to offer greater resolution than VGA. SVGA supports 800 x 600 resolution, or 480,000 pixels.

The SVGA standard supports a palette of 16 million colors, but the number of colors that can be displayed simultaneously is limited by the amount of video memory installed in a system. One SVGA system might display only 256 simultaneous colors while another displays the entire palette of 16 million colors. The SVGA standards are developed by a consortium of monitor and graphics manufacturers called VESA.

XGA

Short for extended graphics array, a high-resolution graphics standard introduced by IBM in 1990. XGA was designed to replace the older 8514/A video standard. It provides the same resolutions (640 by 480 or 1024 by 768 pixels), but supports more simultaneous colors (65 thousand compared to 8514/A's 256 colors). In addition, XGA allows monitors to be non-interlaced.

Reference:

Wikipedia Encyclopedia