I mean, does mac have a "home" folder, and if I want to format and reinstall the system, it'll not affect my home folder? And the Desktop is a folder within the home folder?
OS X does indeed have a home folder, in /Users/<username> with a hierarchy of folders, including one for Desktop, in this location - similar to Ubuntu.
On most Linux distributions the /home is a different partition on the drive and formatting the primary OS partition would not erase your data. This is not the case with OS X and (unless you've made a concerted effort to the contrary) erasing the OS X drive will erase your data.