Merit system implemented almost a month ago,but you just now heared about that.I shows that how much you are lazy and we can predict the post quality of you from this question itslef.

Merit is like an point which will be awarded if you have high quality posts and the posts which gives good contribution to that discussion,so the people may merit you if they feel that is useful to others,and it is for rank up also,you need denifite amount of merit to rank up with the old combination of activity.