The world of computer graphics is a fast paced rat race for supremacy between the worlds 2 largest GPU (Graphics Processing Unit) Nvidia and ATi. From the Rage 128 and the Geforce 256 to the Radeon X2800XTX and the Geforce 8800GTX, the number of video cards is great indeed. The suffixes behind the model names, and terms such as ROP, Pixel Pipelines, Core and Memory Clock Speed can confuse many people buying a video card or making a computer for the first time. This guide is written to help you understand the jargon of shopping for a video card and what video card to get.
=The Core Clock is the frequency at which the GPU operates, and ranges from 350 MHz (Megahertz) to over 700 MHz on the newest models
=The Memory Clock is the frequency at which the Video Card's RAM operates, and has both a realistic Frequency (in MHz and GHz)
=Video Memory is the RAM that the GPU will access instead of System RAM. It ranges from 64 MB( Megabytes) to over 2048 MB, types of VRAM include DDR, DDR2, GDDR3 and the high end GDDR4
=Pixel Shader is the part of the video card that allows individual pixels to have different types of rendering. These range from around 2 to over 96
=AGP (Accelerated Graphics Port) is a Interface port that connects a video card to the motherboard. AGP Cards can transfer at 2x/4x/8x, but is most commonly found in the 8x version. AGP slot cards are currently being phased out, but one can still find current generation cards at higher prices.
=PCI Express is a higher speed Interface port that connects a video card to the motherboard. PCI Express is currently the standard and transfers at 16x.

The Video Cards.
In General, the lower the number on the model the lower the video card is. However, this does not mean a x1300 video card is more powerful than a x850 card from the previous generation. The cutoff is usually at the midrange of the generation, usually the "6" series, (ex. Geforce 6800 Ultra =(performance) GF 7600GT, and Radeon x850XT =(performance) R X1650Pro))) The suffixes are for seperating more than two cards in a single family, (ex 1650 XT/PRO). In general, for ATi cards, the closer a Suffix letter is to the end of the alphabet, the more high end it is. (x1950Pro <x1950XTX) For Nvidia Cards, Cards start at the LE, then to GS, GT, GTO, and GTX. Again, generally, the more pricey a card is, the higher the performance is.

The Price Guide
Under 100
Casual (Casual Gamers, Basic 3d uses, Web, CPU Applications)
For under $100, cards will usually have poor performance in current games such as BF2142, Oblivion, and FEAR. However, if you are not a hardcore gamer, do not play games on displays larger than 20", or do not need a powerful card, There are quite a few good choices, and many bad bad cards that are terrible deals. Cards in this range usually feature core/memory clocks of 500/1000 or less, less than 16 PS, and usually feature 256MB of Memory or lessprice
Recommendations

Nvidia Geforce 7300GT or 8300GS (ships in March)
ATi Radeon X850XT

$100 - $150
In this price range, cards will increase in peformance, but is still not recommended for gaming on large screens. Cards in this price range will usually feature an increase of 50 MHz or so from the previous range, and may have up to 512MB of Memory
Recommendations

Nvidia Geforce 7600GT
ATi Radeon X1650PRo

$150 -$175
In this price range, video cards will be powerful enough to play current games at decent resolutions on medium/high settings.
Recommendations

Nvidia Geforce 7900GS or 8600GT (ships in March)
ATi Radeon X1800 GTO or X1900GT

$175- $299
This is considered a mainstream card range. Cards in this range usually have at least Core/Memory clocks of 550/1400 or higher. Often cards will come with 512 MB of GDDR4 memory. Powerful enough to play current games in high settings, and fairly high settings in incoming 2007 games, these mainstream cards are good choices for the smart buyer. Good deals frequently appear for these cards, and prices will only drop, when next generation cards become mainstream.
Recommendations

Nvidia Geforce 7900GT or 7950GT
ATi Radoen X1950Pro or X1950XT

$299+
This is considered a high end market for video cards. Cards in this range feature very powerful and fast GPU's and a price to match. Cards will often have Core/Memory clocks in excess of 600/1500, with the fastest currently being the X1950XTX with an Astonishing 650/2000 MHz. However, the High end of the video card market is also the market that fluctuates and changes the most, with current fastest cards becoming pushed from the top every two months. The only reason to buy these cards is if you require a powerful setup to play every game ever made in the highest resolution possible. It is even possible to link 2 of these cards together in SLI/Crossfire (Nvidia and Ati, respectively) mode to theoritically double your Frame Rate.
Recommendations

Nvidia Geforce 8800GTS or 8800GTX
None for ATi (until March)
Note: the X1950XTX is a high end card, but is not listed because it is the same price as the 8800GTS, yet is inferior, performance and technically wise (all GF8 series feature DirectX10...ATi's X2____ series is also DX10, but is not slated to ship until March) Thus ATi's High end market has been ousted by the Geforce 8 series.

Note2: As technology constantly changes, the prices also change, and the accuracy of this guide is not guaranteed, but is meant to inform the public about different classes of video cards and what video card class is right for them