Polycom RealPresence Desktop is a special tool for video calls, chats and conferences, similar in a lot of ways to Skype and other such programs, but possessing way more advanced settings and features for comfortable, proper and stable video communication.
The program has a simple enough interface anyone who have used a video communication app will recognize and master easily. You register an account, then dial a number or search another user and call him/her. A call or a conference can be set up just the way you want with numerous settings for your audio and video hardware: volume, lighting, etc. You can filter sound with Acoustic Fence to improve the quality of what you hear and remove the noise. When engaging in a conference with several users, you have an almost unlimited number of people who can join the call, and I've seen for myself that the response time and signal speed do not slow down one bit. The program is generally very well made and works with the best and most stable audio codecs out there.
Additional features include advanced settings for connectivity and interaction: you can easily and comfortable connect to devices located and placed in a variety of environment. there is also the option of creating virtual business cards identifying user, location, and title. Finally, there's a tool for recording your calls.
All in all, Polycom RealPresence Desktop is one of the coolest video communication apps I've seen.