Its pretty much like you reply to the person above you and you either type agree OR disagree.
Then You type a sentence and the person below you can reply to it whether he/she agree or disagree.
Example
PERSON1: PS3 is the best console
PERSON2: Disagree / XBOX360 is better
PERSON3: Disagree / London bridge is falling down due to the riot.
PERSON4: Agree / Earth Is Fukin Over POPULATED with 7 billion people
PERSON5: Disagree / Loveforum is full of hateful people, jaded people, and broken hearted people.
SO ON SO FORTH...
Here is my first sentence.
Shark week is over, it is safe to go to beaches or go scuba diving.