When the main VeraCrypt window is closed, the VeraCrypt Background Task takes care of the following tasks/functions:
WARNING: If neither the VeraCrypt Background Task nor VeraCrypt is running, the above- mentioned tasks/functions are disabled.
The VeraCrypt Background Task is actually the VeraCrypt.exe application, which continues running in the background after you close the main VeraCrypt window. Whether it is running or not can be determined by looking at the system tray area. If you can see the VeraCrypt icon there, then the VeraCrypt Background Task is running. You can click the icon to open the main VeraCrypt window. Right-click on the icon opens a popup menu with various VeraCrypt-related functions.
You can shut down the Background Task at any time by right-clicking the VeraCrypt tray icon and selecting Exit. If you need to disable the VeraCrypt Background Task completely and permanently, select Settings -> Preferences and uncheck the option Enabled in the VeraCrypt Background Task area of the Preferences dialog window.