Google groups can be considered as a big forum, which is broke into diverse topics. It is easily possible to discuss online with other users or to trade emails. In every group there are some hundred topics. Every user can search for the relevant topic with a simple search function. If you want to use Google groups you have to have a Google-account. The registration for such an account is free. You can create your own group and you can establish your own discussion-forums to certain topics. In this huge community there is a certain grade of protection of your privacy and a protection against address-collectors (spam-providers): you have the opportunity of hiding your E-Mail-address (viz. other users won’t see your address, if you don’t want to publicize it).