The Animate transitions between destinations documentation details the four types of animations:
- Entering a destination
- Exiting a destination
- Entering a destination via a pop action
- Exiting a destination via a pop action
“Entering” refers to the destination that is coming onto the screen, while “exiting” refers to the destination leaving the screen.
Therefore when you navigate from destination A to destination B, the entering destination B will have the enterAnim applied to it and the exiting destination A will have the exitAnim applied to it.
When the user hits the system Back button, going from B back to A, the reverse happens: the entering destination A will have the popEnterAnim applied to it and the exiting destination B will have the popExitAnim applied to it.