Regardless of a discussin group's size, there are generally a number of subscribers who follow the discussion, but choose not to participate in it. These are the lurkers. Generally speaking, it is best to lurk for a while after subscribing to a new list in order to familiarize yourself with the group.
A lurk is a person who goes around looking at all the Usenet newsgroups or chat rooms without participating in the conversation or posting a message. However, the negative connotation that we apply to the word does not necessarily apply online. Most people lurk when they are new to a group until they are familiar with the scope or the rules.
to read and observe the going-ons of a public discussion without posting or contributing to it.