If you didn't have to buy it, good.
Here's some simplified clarification:
Bus Interface: What type of slot it's built for. PCIe cards are both ways compatible, so even a modern PCIe 3 type card should work in a PCIe 1 slot and a type 1 card in a type 3 slot. Of course the speed is along the slower one.
GPU Class: Desktop, Laptop, whatever type computers it's designed to fit in.
Core Clock: Core is the processor of a video card. It does the calculation. The clock rate tells how many calculations it can make in a second. MHz means Million cycles per second.
Memory Clock: How many times in a second the memory can store and deliver data. Think of it as writing Post-Up notes and finding, reading and wiping them when needed, a Billion times in a second.
Maximum Memory Supported: How big a pile of Post-Up notes the card has.
DirectX: Which is the latest version of DirectX the card supports. Tells a little about age, too, but that's not a big issue unless you're trying to play a very modern game with a very ancient computer - in which case you'd encounter other issues already.
OpenGL: Basically the same as above. Another method.
Max TDP: How much power your card theoretically uses.
First seen on Chart: Q means Quarter of the said year. Thus Q2=April, May and June.
# of Samples: How many cards they've got information about.
G2D Rating: How well the card performs in regular tasks such as Windows Desktop, Fonts etc. If you have issues there, it's most often because of a bottleneck somewhere else in your system.
G3D Mark: How well the card performs in game like benchmark testing, the bigger the value the better. Note that the result is valid only for the benchmark program used.
