GREX has many interesting conferences, and you can participate in as many of them as you like.
An item is a specific discussion started by a GREX user about an idea related to the conference's main subject.
A conference contains many items. After you read an item, you can make your own response to it if you choose. Items become a permanent part of the conference, and can be read at any time by any interested GREX user.
A response is a comment added to the end of an item. Over time, an item may collect many responses.
You can easily scan what's new in the discussions; review things you read earlier; and filter out areas of discussion that you don't find interesting.