My summary page missing Backup section?

iPods (that are not for iPod touch) do not have a backup function in iTunes. The backup function in iTunes is for iOS devices (iPhone/iPad/iPod touch) only. For traditional iPods, your data is technically already "backed up," because the media files on iPod are in the iTunes library used to sync iPod. What you need to back up is the iTunes library on the computer.

Are you asking how to back up your iTunes library? Since you use a Mac, the best way to back up "everything" (not just your iTunes data) is to use the built-in Time Machine with a large-enough external drive. Time Machine backs up any changes (to whatever is being backed up) every hour, so your backup will be up-to-date to within one hour. And the most powerful capability of Time Machine is being able to "go back in time" to any archived state, not just the latest backed up state. For example, let's say you mistakenly deleted some songs from your iTunes library, but you don't realize it for a few weeks. You can use Time Machine to "go back in time" to an archived state when those song files still existed in your iTunes Media folder, and restore the files. Then, add them back to your current iTunes library.

If you want to only back up your iTunes data, this document describes the process.

Back up your iTunes library by copying it to an external drive - Apple Support

To summarize, you first "consolidate" all of your iTunes media files into your iTunes folder. For a Mac user, if you use the default settings in iTunes, all of your iTunes data should already be in your iTunes folder (but it doesn't hurt to do use the Consolidate files command). Then, copy that iTunes folder to an external drive. If you ever need to restore your iTunes data to a new OS X system, copy that iTunes folder back to the internal drive to replace the "blank" iTunes folder. Unlike using Time Machine, this backup is a "snapshot." It is only up-to-date when you perform the procedure. The Time Machine archive is up-to-date every hour.