Its called the User Reputation System. When someone likes what you post, they "give you rep" by pressing the middle button of the set of three little buttons below your avatar and profile info. The number of points you get from that depends on who the presenter of the rep is. The more senior that member (amount of rep themselves, number of post, and several other secret recipe ingredients that mere mortals like ourselves are not allowed to know) the more rep points you get.
Rep can be positive or negative. If someone is consistently dishing out bad advice or generally behaving badly on the forums, you can give negative rep. The reduces the receiver's rep count.
The idea is to promote good behavior and provide a recognition vehicle for members whose input is generally considered sound.
So, get out there and start helping people! The more value you provide, the more rep you get! Thats the idea anyway.
Of course, the operation of the rep system overall is always a source of discussion/controversy, as you would expect, but for most people, it would seem that it does the job.
Hope this helps. Give me rep if you liked it, just to try it out. I have given you some rep as an example. To see your rep count, look at the top of the page and find the item called Profile. Click that and you will be taken to a page that shows your current rep count and any comments folks have submitted along with it, as well as lots of other useful information!
Enjoy Mac Forums!!