This is a quantitative alternative to other methods of expressing reaction to content, like writing a reply text. Some websites also include a dislike button
The like button was first announced as a FriendFeed feature on October 30, 2007 and was popularized within its community. Later on the feature was integrated to Facebook before eventually FriendFeed was acquired by Facebook August 10, 2009.
The Facebook like button is designed as a hand giving "thumbs up". It was originally discussed to have been a star or a plus sign, and during development the feature was referred to as "awesome" instead of "like". It was introduced on 9 February 2009.