A trending topic is a word, phrase or topic that is posted (tweeted) multiple times on the social networking and microblogging

Microblogging

Microblogging is a broadcast medium in the form of blogging. A microblog differs from a traditional blog in that its content is typically smaller in both actual and aggregate file size...

 service Twitter

Twitter

Twitter is an online social networking and microblogging service that enables its users to send and read text-based posts of up to 140 characters, informally known as "tweets".Twitter was created in March 2006 by Jack Dorsey and launched that July...

. Trending topics become popular either through a concerted effort by users or because of an event that prompts people to talk about one specific topic. These topics help Twitter and their users to understand what is happening in the world.

Controversy

There have been controversy surrounding the Twitter trending topics: Twitter censored hashtags that their users found offensive. Twitter censored the #Thatsafrican and the #thingsdarkiessay hashtags after users complained that they found the hashtags offensive.

Changes to Twitter's design

Twitter's 30 March 2010 blog post announced that the hottest Twitter trending topics will scroll across the Twitter homepage. Users will also be able to find out why a specific topic got to be a trending topic.