Time Machine will back up everything on your Mac....minus a few temp files and trash items....unless you Exclude the file(s) from backups in Time Machine Preferences / Options.
The idea here is that in the event of a hard drive crash on a Mac, the user will be able to restore his Mac exactly the way it was before the crash.
Click the Time Machine icon at the top of the Mac's screen
Click Time Machine Preferences
Click Options
Click the + (plus) button
Navigate using the Finder like interface to select the file that you want to Exclude from backups
Click Save
Do the same for other files that you want to Exclude. This may be a tedious process depending on how you have your files setup, but you will only have to do it once.