Hey Sadia, good question

Basically when a user writes something you like or dislike you can give them positive or negative reputation points which are indicated by the little blue square under your name next to any post you write. When you get more and more positive reputation points for contributing to the forum from other users, you get more blue boxes next to your name and its just a way to show how 'experienced' or 'knowledgeable' you are on the forums.

Just for asking the same question probably a bunch of others are wondering about, I'm going to hook you up with some reputation points.

By the way, to add reputation, just click on the little blue square button near the bottom left of a user's post, next to the green/blue light indicating whether they are online or not.