When lots of people are tweeting about the same thing then it became a trend in the trending section of twitter.com.
Twitter is a micro-blogging platform where you can express anything in just 140-character.
so that your words should be very compact and clear within 140-character.
that’s why some people like Twitter because viewers can easily right 140-character tweets.
also when lots of people writing about the same thing then Twitter show most use keyword as a trend on the trending section of Twitter.
most users try to use # before any trending keyword that’s why it’s called hashtags or what the hashtags are trending on Twitter.
trend.earnfo.com is the best website for checking what is trending worldwide.
not only that if you want to check what is trending on Twitter India then you can also find it at trend.earnfo.com.
in simple words when lots of people are writing the same keyword on Twitter it became a trend.