Cisco WebEx is a web service for online meetings and and collaboration. WebEx has been acquired since 2007 by Cisco company.
You can invite other people, schedule meetings, share files (documents, videos, pictures etc.) and view files shared by others. Other people can view your desktop, if you want, to watch real time demonstrations or data from your computer.
You can share only specific applications, for example Chrome browser, if you want, and keep the rest of your desktop private. The free version has limited functionalities, but they have good pricing plans for advanced features, compared to similar products, like GoToMeeting.
Allow others to control your PC or control computers of other participants. Use chat and view image or record video in HD resolution.