OSX demystifies the Unix file structure somewhat by adding a few extra folders that everything goes into. Like your installed applications go into your /applications folders, your settings and whatnot go into one of your two /library folders, and so on, and so on. But with Linux and BSD, hell...if you install an application, you don't know where it's going. One of the various /bin or /sbin folders, but which one? Up until 556fmjoe showed me...
...it used to take me forever to find where an application went on Linux.
Windows? Your applications are going into Program Files. Dll files and libraries? System32 and/or WoW64. Your personal settings? Users. OS stuff? Windows. It's pretty straightforward.
Now I'll admit that some of my problems with one, and ease with the other might be due to familiarity and a lack thereof. But at first glance, the 'nix directory structure is anything but self explanatory. It's almost a maze of weirdly named stuff.