Badges are fun. They prove that you know the information, and you can compare the number of badges you have with your friends and peers to see who is doing best.
Employers:You can even share your badges with employers who might want to know that you have acquired the proper education to do the job you have been considered for.
In order to receive a badge a user must pass a quiz for a lesson in that category. For every quiz that a user passes he will receive a badge, so if a user passes 10 quizzes in the category of mathematics the user would receive 10 badges for that category. The more badges a user has for a particular category the more quizzes he has passed and the more information he probably knows about that subject.
Sub-category badges prove where your focus is. If you have 10 badges in mathematics, and all of them are in Algebra, then we will know that you have skills in Mathematics with a focus on Algebra.