Basically, the Media and Media Sub Type is what's used to categorize your media. First, all of your Movies, TV Shows, and Home Video get assigned the Media Type "Video". Then you break this group down into Video Sub Types such as Movie, TV Show, etc. Usually this is done automatiically (for the most part) when you import the files. MC (latest versions) are good about figuring out what you have (and you can tell it how to assign the categories based on what folders you are importing from (Tools>Options>Library & Folders > Configure AutoImport).
If it is not done automatically you can fix things in the Standard View. For Video, open the Video>Files view and see if all the data is showing (i.e. Media Sub Type) for each file. You can edit/add what is missing. If the coulmn you need is not shown, just right click on the header and select it from the drop down list.
The "Fill Properties from File Name" is used, for example" when you import a file with a name like "Lost s1e01 Pilot.mkv" and you use that Fill feature to separate the file name into the correct data cells for Series, Season, Epoisode No., Episode name, etc. However, the current version of MC17 does this automatically (and is pretty good at it) so you really only need this if you name your files something unusual when you rip/copy them or if you already have files in the database (prior to the new feature) without correct info and now you want to go back and fix things.
Here is a screen shot of the Satnd View>Video>Files: