Q: What is the difference between Save As, Render As and Make Movie in Movie Studio?

Answer: Save As and Render As are two totally different functions - you need to do both for ALL projects.

Save As only saves the Project File.

Save As and selecting Copy media with project saves the Project File and a copy of all Video, Images and Audio files you may have used.

Save As has nothing to do with creating/exporting/rendering a new video from your project.

Render As or Make Movie is what you use to create/export/render a new video of your project.

If you used the New Project Wizard at the beginning of your project and filled out all the fields, Movie Studio creates a folder structure for your Project file, Media and Rendered Videos to live in.

If you DON'T use the New Project Wizard, you need to manually check and set the output folder location for where your Project Files and Rendered Videos will be saved to. This is the step that gets all new users into a giant mess. When you don't check the Save In output folder addresses, your files are probably being saved in all sorts of random locations on your computer, that relate to different programs and folders you were using when NOT using Movie Studio.

I showed most of this information in this old tutorial here:
How to Render 1080p Video using Sony Vegas Movie Studio HD Platinum 11