Listen (in the top bar) plays a listening copy: a render of your program stored for this device, so it starts instantly and keeps playing on a locked phone, with lockscreen controls and a sleep timer. The copy is per device and re-renders free after changes. Your exported WAV or MP3 remains the file you keep and take anywhere. Note: the listening copy is compact audio, so if the silent layer matters to you, listen to the lossless export.
The in-app listening copy
The Listen player renders a listening copy of your program for this device, so it plays instantly, on a locked phone too. It is per device; your exported file is the one to keep.