What is a Discussion?

An extended communication dealing with some particular topic and with other member's interaction.

Example:

If you want to start a discussion on "I want to buy a mobile. Is Nokia 6600 is good?"
A member may reply "You can go for that model, as that model has built-in mp3 player and ability to install thirdparty softwares"

Another member may suggest you another model with different features.

So, after the discussion you come to one conclusion to take a best one.