Microsoft uses the Click-to-run Technology for deploying Office 365 Applications on a Computer. One of the main features of Click-To-Run Technology is that a User can begin working on an Application even before it is fully downloaded something which is not possible with the traditional MSI (Windows Installer) Model. It is similar to streaming content on YouTube. One does not wait for the whole video to download before viewing it. A user can start watching the Video even if it is still downloading.
Applications deployed using the Click-To-Run Technology require the Internet for Activation. It cannot be deployed on Shared Computers using Remote Desktop Services or on Windows To Go Usb Devices.