The rewards mentioned next to the quests' names mostly indicate the amount of Renown and Gold given to you from the Guild for the fact of completing them; there are a lot of experience and alignment points, weapons and items to be obtained during the quests, but their amounts depend on your decisions and actions. The renown and gold values written below are only some kind of minimum, then. You mostly get a lot more for completing the mission than this.
These missions are called "optional quests". You agree to do them by taking the certain Quest Cards from the Guild. They are mostly rewarded with Renown and Gold. They're mostly quite simple and short, so it pays off to do them all. There aren't many of them after all.
Doing the blue quests gives you positive alignment points.
Doing the bronze quests gives you negative alignment points.
Doing the black quests is either neutral to your alignment or so flexible, that the type of points you get varies depending on the actions you take.
These quests are found throughout all Albion and mostly require you to solve some local people's problems or just collect some useful stuff. Nothing big, really. We don't get any Renown or Gold from the Guild for completing them. In most cases the rewards are worth the time, though