Huge, Hidden Space in User Folder?

I am trying to free up space on hard drive of MBA. previously asked about deleting iMovies, since don’t use and takes up 3GB of space. https://discussions.apple.com/activity?streamSource=connections. Pretty much told to do many other things. I have nothing in iTunes; moved almost all photos to external, and iPhoto is only 1.4 GB. Emptied all trash.

User folder says it is taking 19 GB, but its individual folders of Desktop, Documents, Download Movies, Music Pictures and Public add up to only 1.5 GB. What is taking up the other 17.5 GB?

I am running Omni Disk Sweeper, and it shows that fourth largest item is “private”, 5GB. What is that?

Found this info, http://pondini.org/OSX/LionStorage.html. It says that each user folder has such things as email, contracts, calendars, etc. (below) Could those be what’s taking up space in User? If so, it means that I wasted a lot of time to save a couple of GB of photos. Worst, also means that Apps, System, App support, and hidden space of User, pretty much take all my space (48 GB of 60 GB).

In each User home folder:

1. •Preferences and settings
2. •Downloads
3. •User caches and logs
4. •Word processing documents, spreadsheets, etc
5. •Email and Contacts
6. •Calendars
7. •Browser history, bookmarks, cookies, web site icons
8. •Keychains
9. •Widgets
10. •Data for any apps that doesn't fall into one of the categories above
11. •Files supporting various apps