There can be hundreds of them, from the top of my head; the major ones could be
1. For Education
2. For HR & Recruitment
3. For Customer Feedback
4. For Sales
5. For Personal Blogs
6. For Medical Facilitations
7. For Public Service Communication
8. For Customer Support, etc.
An invaluable time saving: no need to travel for the first commercial meetings for example.
Share experience, ideas, create a remote link.
It can be a learning tool, a collaborative tool or a sales aid.
The list is quite long! A great tool in which I decided to work ;)