Note the difference between saving a drawing as a Template, and saving a drawing as a 3DD Document with the Save command: 

• The Template function only saves the file names and other settings so they can be retrieved at a later time.  If the Template file ( with the .sw3dt file extent) is moved, all the file used in the template (such as the topographic grid file, field strength data file, boundary files, etc.) must also be moved.  Without those files, the template will not be able to find the information needed for the image
• The Save function, which saves the drawing as a 3DD document (with the file extent .sw3dd) is completely self-contained.  As a result, the file size will be larger, but the entire drawing can be moved or sent to another 3DD user simply by transferring the single .sw3dd file.

As a general rule, if you want a drawing you can easily load later on your own machine, saving as a Template will be faster and create a smaller file and would usually be preferred.  On the other hand, if you are creating a 3DD image you want to send to another 3DD user, you can use the Save function to create a single file that is easily copied or sent via email.  The  .sw3dd file can only be opened and viewed (and edited) by the 3DD program.  If you want to send an image file that can be viewed (but not edited) by many browser or viewing programs, you should use the Export function to create a JPEG or other standard graphic format.