A template is a very productive way of reusing modified Inventor files. For example, LENGTH, WIDTH, and THICKNESS iPropertes for woodworkers that normally create cutlists. Or you can have a company standards FX part pre-inserted (something I do). If you only work with a certain material, your template file can have that material already applied. You get the gist.
You can literally have hundreds of modified part, assembly, drawing, presentation, and weldment template files that are preconfigured for a certain client, a certain work-flow, or what have you. As I told a reader In the comments yesterday, I keep folders of template files for specific companies that I subcontract for in an archive, and when I again do business with them, I drop their folder into the Inventor Templates folder and voila!
The folder creates a new tab in the New File dialog in Inventor, the tab has the same name as the folder, and everything in the folder shows up as a template! Personally, when I am done with a project, I move the folder again to reduce clutter, but you can organize templates however you wish for your own manufacturing processes or personal preference. Whatever trips your trigger—just make sure you keep a copy of the original templates safe somewhere. The location of the template folder on a typical single user install is:
C:\Users\Public\Documents\Autodesk\Inventor 2012\Templates\
If you are in a corporate or other setting with an IT department, you need to talk to them. Tell them Mark sent you. Later.
