1) everyone has a different answer to this, and i'm often confused myself as to the functional purpose of it. to the best of my knowledge, selvage denim is higher quality because it is made on the narrow 29 inch looms. Japanese companies bought out most of these in the 80s i believe, but after the premium denim trend started to unearth, some us and european manufacturers started using the narrow looms as well. selvage denim costs more to produce, and requires more cotton to create. many jeans these days use selvage denim (including some GAP jeans, some A&F jeans), but only some companies put special care into making a very nice selvage seam. Evisu, Denime, John Varvatos, APC, Nudie, Kunna are examples that make especially nice looking selvage seams. paying extra for selvage jeans is a personal decision, mostly only hardcore denim aficionados require heavy weight (14-16 oz) selvage denim; but of course their are exceptions such as LA guy who prefers lighter weight. the texture of selvage denim supposedly looks and feels different after the jeans have been worn in, but i'm not going to claim infallability here, as many would argue that there is no difference. the most obvious aesthetic difference is the nice looking selvage outseam that can be seen when the jeans are cuffed at the bottom, and the thick fading lines down the sides of your jeans when they are broken in or acid washed. i guess you could say that selvage denim is jean's equivalence to a fully canvassed suit. 2) dual ringspun (ringxring) is when both the warp and the weft cotton is ringspun. you can see a clear difference when looking at the underside of the jeans.