This is probably not the best place to ask, but anyway, reputation is exactly what it means. If someone wants to congratulate you on a your post or thread, then they can give you a "reputation" point, which will increase your reputation in the forum with other members. You can also give other people reputation points, and the rep power measures a quantity of your rep.
If you want to become a full member, then you have to give a minimum of 50 posts or more. You can check how many posts you have on the left side, of where you just posted, where it says "Posts: 12".
If you want to become a full member, then you have to give a minimum of 50 posts or more. You can check how many posts you have on the left side, of where you just posted, where it says "Posts: 12".