What is the difference in these Video cards?

There's so many differences, that there's no point in trying to explain them all.

What you need to understand is that all of those numbers would be sorely out of date, and probably not worth getting except for cheap.

Why? Because Nvidia is currently on the 600 series. That's 4+ generations from those card.

If you want to know what's best for you, you know your needs, and your budget. If you want to know how to tell within a generation, it's pretty simple.

First number is the generation, currently 6 or Nvidia. 7 for AMD. The second number is for the level within the graphics performance, for example 610-640 entry level for Nvdidia. 650 is where it starts to get for gaming. 670, 680, 690, are the extreme numbers. Sometimes Nvidia and AMD have a bit of an extra like GT, GTX, Ti and such, but don't worry too much about it. You can look that up as you will.

But don't try to understand all the differences, just learn what you need and what you care to spend.

Anything ending in M is a small mobile gpu and will be half as fast as a non-M version.

For NVIDIA the 4-digit series are very old. The 3-digit series are current (the best being 680 for desktops and 680M for notebooks).

Cards under x5x are generally not useful for gaming. The first digit is generation. 2nd is "grade". 3rd digit is rarely used to indicate a small difference.

NVIDIA doesn't seem to follow its own naming scheme very well, as the 670M/675M are still using last gen tech. Though they are still faster than the 660M and slower than 680M.

depends on what you are looking to do. I do some gaming, but not that into it. I use a 8800GTS 640MB card, and it does the job just fine. If you are like me, spend around $50 on a used card made by either EVGA or XFX. If you are going for extreme gaming, Nvidia went around the number scheme. GTX6xx is the newest, but I have a gtx 550ti and it is plenty