Radeon HD 

A line of video cards made by ATI and the next series after the standard Radeon series. These video cards are typically stronger, faster and have more features such as Eyefinity, ATI Stream, and Avivo HD. However, the latest cards are relatively large and quite expensive. The latest is the HD 5970 which is known as on of the fastest cards to date. The latest series in the Radeon HD line is the 5XXX series which was meant to have Microsoft's DirectX11 integrated and widely available on the market.

Man: "Dude!!! I just got a Radeon HD 5970 for my computer!!! It's gonna pwn some ass!!!"

Friend: "Do you have a full tower case to fit it in?"

Man: "..... @%$#!!!"

Radeon HD by mistahskinnymahn June 23, 2010

Radeon HD 4650 

A graphics card that people should buy if they're on a low budget; it's the one card that won't get you broke out of your mom's money

Friend 1: Hey dude, check it out - I got a $100 GT 520 for $95!

Friend 2: Well I got this Radeon HD 4650 for $30 and it blows your 520 out of the water

Friend 1: Fuck your mom, man

Radeon HD 4650 by computer_geek42 January 20, 2013

ATI Radeon HD 5870 

An ATI graphics card that was released to the public in 2009.
It currently runs for about $149 online.
In the Apple Store it is $299.

In the Apple Store it was released in Late 2012.
To a Mac-Pro owner, they believe Apple is rewarding them with state of the line 1 GB DDR5 that does not perform even close to a workstation graphics card, but they don't do their research.

Mac User: Omg a Brand ATI Radeon HD 5870 I am going to play Photoshop!

Windows User: I am playing on my new ATI Radeon HD 7970 3gb for half the price.

ATI Radeon HD 5870 by Fancy Linux Penguin December 8, 2012