User-generated content (UGC), alternatively known as user-created content, is any form of content created by users of a system or service and made available publicly on that system - wikipedia 
UGC most often appears as supplements to online platforms, such as social media websites, and may include such content types as blog posts, wikis, videos, comments or ecommerce.
Studies of UGC break the audience into three segments: - Power users - Casual contributors - Lurkers
# Breakdown
When you plot the amount of activity for each user, the result is a Zipf curve, which shows as a straight line in a log-log diagram.
The term "user-generated content" and concept it refers to entered mainstream usage in the mid-2000s, having arisen in web publishing and new media content production circles. The BBC adopted a user-generated content platform for its websites in 2005, and TIME Magazine named "You" as the Person of the Year in 2006, referring to the rise in the production of UGC on Web 2.0 platforms.
# Links
# See also * Definition * History * Motivation for creating UGC * Ranking and assessment * Types * Effect on journalism * Use in marketing * Criticism * Legal problems * Research - Events - Participation inequality - 90–9–1 rule