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Video cards (video boards / video display boards / graphics cards / graphics adapter) is a physical hardware circuit board(s) which connects to the Motherboard. When the video card is connected to a monitor it serves as the visual link between you and your computer, allowing you to view and manage your computers software data.

VGA (Video Graphics Adapter)
use to connect analog monitors

DVI (Digital Video Interface)
use to connect digital monitors

HDMI (High Definition Multimedia Interface)

Built-in to the motherboard (Integrated Video Card)

PCI-e (The fastest and the most expensive)

AGP (Extremely Fast)

PCI (Fast)

ISA (Cheap and Slow)

Type of Bus	Bits Wide	Transfer Speed

ISA	8 bit	2.38MB/s
ISA	16 bit	8MB/s
PCI (Client)	32 bit	133MB/s
PCI (Server)	64 bit	266MB/s
AGP 1x	32 bit	266MB/s
AGP 2x	32 bit	533MB/s
AGP 4x	32 bit	1,066MB/s
AGP 8x	32 bit	2,133MB/s
AGP 8x (high-end)	64 bit	4,266MB/s

PCI-e
Lane Widths	Peak unidirectional bandwidth	Peak full duplex bandwidth
x1	250MB/s	500MB/s
x2	500MB/s	1GB/s
x4	1GB/s	2GB/s
x8	2GB/s	4GB/s
x16	4GB/s	8GB/s
x32 (new)	8GB/s	16GB/s

Video Memory

32MB is a typical Video Memory if you are into gaming you will need more or you’re going to run the new Vista OS you are going to need at least 128MB
If your a gamer 512MB or more is needed to play those complex games

High End Video Card sometimes contain their own BIOS, memory, cooling mechanism, processor, S Video connector and a TV Tuner connector for connecting your video card to your television. SLI nVidia Scalable Link Interface use for combining video cards ATI calls their Crossfire

Direct X - is a collection of API’s for handling tasks related to Multimedia and Microsoft Platforms.

Types of Video Memory	Speed
VRAM	Fast (Obsolete)
WRAM	Fast (Obsolete)
SDRAM	Fast (Low End PCI/AGP)
SGRAM	Very Fast (PCI/AGP)
DDR-SDRAM	Very Fast (High End PCI/AGP)
G-DDR2-SDRAM	Extremely Fast (High End AGP/PCI-e)
G-DDR3-SDRAM	Extremely Fast (High End AGP/PCI-e)
G-DDR4-SDRAM	Extremely Fast (High End AGP/PCI-e)
G-DDR5-SDRAM	The fastest video card (High End AGP/PCI-e)

VGA vs. SVGA vs. XGA

All video cards use VGA routines to generate basic display to interact with a PCs system BIOS. Then, any advancement on these routines with no universal standard to speak about, to generate display and color above 640x480 with 16 colors is considered SVGA or XGA. I believe I can state without exception all video cards sold in nearly a decade would be considered SVGA or XGA (LCD and Laptops), capable of displaying a larger realm of color and resolution than basic VGA or 640x480 - 16 colors.

Video Memory vs. Video Speed

One of the most misunderstood components of a video card is the Video Memory. Video memory does not equate to Video speed. Video speed is determined by two major factors: the chipset on the video card and the I/O slot holding the video card, (ISA. PCI, AGP, PCI-e). Video memory only determines the ability to display a certain color depth and resolution, such as 800x600-16million colors. There exists a mathematical formula to determine the required amount of memory on a video card to display varying degrees of color and resolutions, but let us suffice to say that a four (4MB) video card can display 1024x768-16million colors all that is required to work with photographic 2D images. Since it is rare today to find any video cards with less than 4MB/s of memory, this is not really much of an issue.

Video Card Default Resolution and Color support

VGA video graphics adapter
Resolution and Color Support
640x480 16
320x200 256

XGA extensive Graphics Adapter (LCD and Laptops)
Resolution and Color Support
800x600 65,536
1024x768 256

SXGA Super XGA
Resolution and Color Support
1280x1024 65,536

WSXGA Wide Super XGA
Resolution and Color Support
1680x1050 65, 536

Color Support in Bits/Pixel Measurement

16 colors = 4-bit color
256 colors = 8-bit
65,536 colors =16-bit (high color mode)
16,777,216 = 24-bit (true color mode)
True colors = 32-bit (usually reserved for scanning)