Above, you'll see a picture of a random post I picked just for an example. I suggest you enlarge it for a better view. Look at the circled area. There is plus sign (+) and line sign (--) and and a minus sign (-).
Using these signs, you can cast a vote for that post you are viewing. Members get reputation points according to how you use this feature.
So, if you like a post, show your appreciation! It only takes the point and click of a mouse!
Enjoy!