For the purposes of this site, these are the roles you may see discussed.
The server administrator can configure the hardware and web server software.
The wiki administrator can edit configuration files and also knows the admin password, which is used for site administrative tasks.
An editor is an author who can publish pages. An editor knows the "publish" password if there is one. All editors are authors. Typically all authors are editors unless a wiki administrator has enabled drafts and set a "publish" password.
An author who cannot publish is not an editor.
The distinction happens when you enable drafts and set a publish password. When that happens authors can only save drafts unless they use the publish password.
Assuming uploads are enabled, an uploader is someone who can upload files (also called attachments).
Uploads can be enabled for all authors or and upload password may be set.