A free app for Windows, by Microsoft Corporation.

If you are looking for an app that will make you more productive, Lync is a great option. Lync is a collaboration and communication app that is used by thousands of people worldwide. It allows you to join meetings in real-time, send instant messages to your colleagues, collaborate on documents, and make calls. With Lync, you can stay in touch with your team no matter where they are in the world.

It is a great app for business and social use. If you want to join a meeting with your colleagues, just press the button and you will be connected.