ResearchGate is the professional network for scientists and researchers. Over 25 million members from all over the world use it to share, discover, and discuss research. RG is guided by their mission to connect the world of science and make research open to all.
I believe RG is primarily a research base. However, as with any online sharing platform, there will be a degree of social networking and interaction. In this case, researchers may recommend others works, ask for advice, assistance and feedback etc. Hence it may also be seen as a learning platform as well.