A ' photocopier '  (also known as a  copier  or  copy machine ) is a  machine  that makes  paper copies of documents and other visual images quickly and cheaply. Most current  photocopiers  use a technology called  xerography , a dry process that uses electrostatic charges on a light-sensitive photoreceptor to first attract and then transfer toner particles (a powder) onto paper in the form of an image.  Heat, pressure or a combination of both is then used to fuse the toner onto the paper. (Copiers can also use other technologies such as  ink jet , but xerography is standard for office copying.) Earlier versions included the  Gestetner  stencil duplicator, invented by  David Gestetner  in 1881. Commercial xerographic office photocopying was introduced by  Xerox  in 1959, and it gradually replaced copies made by Verifax,  Photostat ,  carbon paper ,  mimeograph machines , and other  duplicating machines . Photocopying is widely used in the business, education, and governm

Social media  are  computer-mediated   technologies that facilitate the creation and sharing of  information , ideas, career interests and other forms of expression via  virtual communities  and  networks .  GeoCities  was one of the Internet's earliest social networking websites, appearing in November 1994, followed by  Classmates  in December 1995,  Six Degrees  in May 1997,  Open Diary  in October 1998,  LiveJournal  in April 1999,  Ryze  in October 2001,  Friendster  in March 2002,  LinkedIn  in May 2003,  hi5  in June 2003,  MySpace  in August 2003,  Orkut  in January 2004,  Facebook  in February 2004,  Yahoo! 360°  in March 2005,  Bebo  in July 2005,  Twitter  in July 2006,  Tumblr  in February 2007, and  Google+  in July 2011. Some of the most popular social media websites are  Baidu Tieba ,  Facebook  (and its associated  Facebook Messenger ),  Google+ ,  Myspace ,  Instagram ,  LinkedIn ,  Pinterest ,  Snapchat ,  Tumblr ,  Twitter ,  Viber ,  VK ,  WeChat ,  Weibo