If you want to learn about lenses I suggest you refer to this site;
I find these reviews to be the most involved, thorough, and well researched. I also suggest that you use an online dictionary to look up terms that you may or may not be familiar with. The ONLY thing I don't like about his reviews is that he makes every lens sound like a great lens. So if you want to make the best decision, you need to read his reviews about all different version of brands and lenses and you'll discover that he has subtle differences between lenses that are technically garbage, and those that are supreme.