Classic Mac OS
All preferences are often stored in a unified, centralized Preferences folder in the System Folder. Additional folders may be created inside the folder itself.
Mac OS X
With Mac OS X, the situation got a whole lot more complicated. Generally, system-wide settings that apply for more than the current, logged-in folder are stored inside the Preferences folder inside the Library folder on the root level of the Mac OS X startup volume. Settings for applications on a user-per-user level are stored inside the Preferences folder located inside the Library folder in the user's Home folder.