The plain start text should always be used when communicating with other apps. You can send and receive values from other apps with it! For all other purposes you should use the start value. Use it e.g. when passing values from one screen to another.
When the screen closes, the start value does not change! Use the variable
Screen.Other Screen Closed if you pass values through
Close screen with value!
The close screen with value block triggers both the Initialize and OtherScreenClosed events instead of only the OtherScreenClosed event.