The social networks are distributed across various computer networks. The social networks are inherently computer networks, linking people, organization, and knowledge. Social networking services vary in format and the number of features. They can incorporate a range of new information and communication tools, operating on desktops and on laptops, on mobile devices such as tablet computers and smartphones. They may feature digital photo/video/sharing and "web logging" diary entries online (blogging). Online community services are sometimes considered[by whom?] social-network services by programmers and users, though in a broader sense, a social-network service usually provides an individual-centered service whereas online community services are group-centered. Defined as "websites that facilitate the building of a network of contacts in order to exchange various types of content online," social networking sites provide a space for interaction to continue beyond in person interactions. These computer mediated interactions link members of various networks and may help to both maintain and develop new social ties.