The required level of interactivity & control over the content by the client & the site users dictates if a blog, forum or content management system is going to be utilised.

Blogs
A blog allows mainly textual control of the content & structure. In it’s standard form, a blog script like Wordpress requires image files to be uploaded by File Transfer Protocol (FTP) or modification to allow uploads via a web interface. The level of interactivity from the visitors is limited to comments made on the articles.

Forums
A blog allows more visitor level interactivity but once again, in it’s standard form a forum, such as PHPBB still requires either FTP access or modification to allow image uploads via a web interface.

Content Management Systems
CMS’s allow a client to do virtually anything through a web based administration interface. Using a script like eZ Publish , they can add, move or delete sections, upload images and create new pages almost at will. The restriction on most Content Management Systems is usually the layouts tend to be the same on every site using one.

Community Scripts
Online community scripts usually contain elements of all the above systems to make them viable in terms of client & user usability. However, due to the level of interactivity between the members & administration, community scripts are notoriously complicated systems that require constant monitoring.