The Welcome Visitors page is special. Every site that is created includes this page, and it is the first page you are directed to when you navigate to the wiki's domain. Every lineup will contain a Welcome Visitors page as its first member (unless you manually remove it). You can think of this page as your Home page for the site.
This makes it important and useful to craft your Welcome Visitors page carefully. This page should contain the most useful navigation links that you or your readers might want to use.
There are a number of know problems with the current design of wiki with regard to the --Welcome Visitors__ page. See Welcome Visitors Danger for a discussion of these dangers.