This window is automatically populated by the import procedure. It keeps in memory your selections so that the system knows what to do in the future, it will automatically change it without asking you again. This is especially useful for the spelling of street names, but it is also used to remember your selection for comments, codes and languages.
If you do not want to automatically replace a certain spelling, click on the X to remove the line.
You can also manually add your own different spelling, by choosing the type in the first column, and then indicating what you want to replace. For example: the first line in the screenshot, every time the import finds the street name St Marc, it will show as Saint Marc on your screen