Blue's got the right of it. Reps and Likes are ways to let folks know how they are doing. You can give out as much as the system will allow. It won't let you continue to give the same person rep all of the time, it wants to wait until you give to someone else. The more you give the more you get in general. The more you have the larger the amount you can give will also increase, I think Blue already said that.
It's a good way to judge how long someone has been on the forum and how well they are, well, "respected".
Peace