We can find in the market:

• Web Content management platforms (like Joomla), usually called "Content Management Systems" , will be referred here as CMS
• Conferencing tools (like webex, MS Live meeting)
• Learning management tools (like moodle) , additional common names are  "Learning Management Systems"  (LMS) or "Learning Content Management Systems" (LCMS) or "Course Management Systems" (CMS, confusing term with the CMS from above).  We will refer them here as LMS.
• Social platforms. (like facebook).

What they usually do and what they lack:

In each category of the above, there are dozens of applications in the markets. In this document we will mention the major or best players in the markets, and we will base our examples on those who are considered "top of the line" or have largest market share.