LinkedIn is for professional and business networking.
LinkedIn is the world's largest professional networking site.
LinkedIn allows you to network with people professionally in your industry by "connecting" with them. It also allows you to search for people in a specific industry whose services you might require.
Your LinkedIn page is essentially an online CV, showcasing yourself and your experience, with potentially lots of references. LinkedIn allows you to leave recommendations about other people you know or who you have done business with, and likewise allows them to leave recommendations for you.
Other social media can be "injected" into your LinkedIn page such as tweets and facebook posts.
DBS will set up a LinkedIn profile for you that will look similar to these: