Granting access to strangers
An anonymous user is a wiki visitor that has not logged in. Your first decision to make is whether to allow anonymous users to see the wiki.
For wikis that serve as public web sites, the answer is usually "Yes" but for most internal or not-for-public-consumption wikis, the answer is "No." In other words, the primary reason to require users to log in is to ensure that information is available only to approved individuals.
anonymous users are people that have not logged in to the wiki
public sites usually grant read access only to anonymous users
Even if anonymous users can see the wiki, it's common to require visitors to login before changing content or posting comments. This ensures changes can be traced back to individuals, which in turn can help build personal connections within the community, identify training needs, and dissuade users from posting inappropriate content.
If you decide that anonymous users cannot use your wiki, then the login screen is the only wiki page a user will see until they log in.