SNS (Social network service) - definition
A social network service or social networking service, most often called SNS, is a medium for establishing social networks of people who share interests and/or activities.
Social networking sites allow users to share ideas, activities, events, and interests within their individual networks. Most social network services are web based and provide means for users to interact in various ways, such as e-mail and instant messaging.
Modern internet-connected always-online phones stake a lot on SNS connectivity and integration with the various services getting more popular than ever.