Administrators (aka Sysops) are trusted members of established wiki communities who have been granted additional permissions. These permissions include the ability to delete and undelete pages and images, the rollback command (undoing edits by a single IP/User with a single click), and the ability to block users.
Administrator's edits should not carry more weight than any other editor's unless it is a correction based on policy, which should be noted in the edit summary. Administrators are expected to be available to the community through email, (the Email this user link from their userpage), and to be helpful to other members of the community while trying to accomplish community set goals on the wiki.
Administrators are expected to act as mediators in cases of user disputes, and are expected to act in a professional manner within the editing community.