1.0 to 1.5 qt/lb is the range most brewer's shoot for. I tend to be right at 1.2 qt /lb most of the time. 1.0 qt/lb tends to get a little thick sometimes making it more difficult to stir your mash.
Unless you have some other volume management issues going on, shooting for the middle of the range is a good place to be.
In lay use, I tend to think of conversion as the actual process of turning the starches into sugars. When I think of extraction, I tend to think of some sort of quantification of the process itself. But really this is usage. I'm sure someone will specify - with scientific backing - that extraction is pulling the starches from the grains, and conversion is the enzymatic reaction that converts them to sugars - or something along those lines.
Whether you are "extracting" or "converting" starches, at the end of the session you wind up with fermentable wort, and that is what it is all about.