4. SHARING INFORMATION

We can define social networks as virtual environments for communication, interaction and the sharing of resources.

4.1.Horizontal social networks

The most popular examples of horizontal social networks are:

·Facebook, that allows groups of 'friends' to public messages (public and private) with texts, links, photos, news and videos.

Facebook can also be used by companies to give information about their activities, advertise products... In 2014, Face book had a toal of 1.350 million of users.

·Twitter, the social network that has some inusual features, such us the tweets (shorts messages, with no more than 140 characters, called microbloging). You follow the tweets of another user, and that person might not follow you

·Google+, that allows users create 'circles' of friends in order to share information.

4.2. Vertical social networks

The users of these social networks form communities who have similar reasons for using the application, which are:

-Sharing professional information, that LinkedIn is the most poplar.

-Sharing general information, FriendFeed is a popular example.

-Sharing photos, Instagram, Flickr, or Pinterst are popular.

-Sharing videos, Youtube, Dailymotion or Vimeo are common examples.

-Live streaming, Skype, Livestream, and Twitch.tv are often used.

- There are many other services related to sports, cinema...