How many types of rice are there?

Rice was not really part of my life growing up. We had what I guess would be considered typical American food when I was growing up. There were 4 kids so the menus of spaghetti, pork chops, mac n cheese, fish sticks, and the occassional roast beef that us kids hated but was a favorite of my Dad was the menu. I don't recall a single instance growing up where mom prepared rice for us and we only very rarely ate Chinese food.

Even once I was out of the house and in college I almost never had rice except for that brief period of time where the various industries convinced us that "low fat" was the way to good health so i bought some minute rice and promptly made it wrong even though they make it really easy for you.

Living in Thailand for the past year, it should come as no surprise that a great deal of my diet is comprised of rice. Virtually every meal is rice-based and that is just fine with me. However, it wasn't until I was at the market the other day and ventured down an aisle that I never visit that I saw this:

I wouldn't even know where to begin as far as evaluating the quality of each of these is concerned. Basically, the only type of rice that I know is "white" and "brown." I think i can presume that the most expensive one is the best one and would be a complete waste of money on my part since I only have a very rudimentary understanding of how to prepare any of it and would likely do it wrong.

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While many types of them are grown in a similar fashion (as far as I know) the types of rice paddies that I see in Thailand all seem to have a similar layout.

As it turns out there are a whopping 40,000 types of rice on the planet presently, but the actual possible types of rice is unknown and the International Rice Gene Bank has 90,000 strains stored in its vaults.

I can tell that some rice is different than others depending on how nice of a restaurant that I am eating at but this figure of nearly 100,000 types of rice existing just blows my mind.