.dba - the actual source code to your project
.dbpro - a file with data that helps the editor manage the data that would not normally be in your code. eg the paths to the executable, notes about your game, etc.etc.
.exe an executable file that is your source code compiled ready for anyone to use.
.bak a copy of your .dba file in case you make a mistake, but only from last compile.
if you cant see any text when double clicking a .dba file open that file by right clicking it and opening it with notepad, you can see that there will be data in it unless the dba file is like 0 bytes in size.
your mime type associations within your computer need to be adjusted.
right mouse click a .dbpro file and associate it with the dark basic editor.