There are a lot of denim weights being thrown around. Here is a quick chart to help you understand the basics. 

Weight in oz. (technically ounces per square yard)Basic Description
8 oz.Really light weight. Will not be durable. Won't require much, if any, breaking in. Not a good option for a denim jean.
10 oz.Light weight. A decent summer weight. Will be easy to break in and comfortable to wear. Not a good all purpose or work jean option.
11 oz.Semi-light weight. Decent for a lighter weight jean. Will not be very durable in the long run. 
13 oz.Medium weight. Good all purpose weight for standard jeans. The most common historical weight of denim. Newer denims tend to be a little lighter (less cotton = lower cost).
14 oz.Medium + weight. A good durable weight for denim. Will last for a long while. Will require significant break in, but will be exceptional when broken in.  
16 oz.Heavy weight. Pushing the boundaries of conventional denim weight. Sometimes considered a lightweight armor. Will be a bit of a bitch to break in. 
20 oz.
Super heavy weight. Uncomfortable. Extremely durable. Very stiff and will take 1+ year to break in. Can be done, but only for the brave of heart. 
23+ oz.
Novelty. Not recommended. You will not be happy with a pair this heavy. Can actually cause wear marks and bleeding on the hips while being broken in.