A property list file (.plist) is a small file that is usually used by an application to save a user’s settings or preferences. They are an important part of Max OS X and date all the way back to Steve Jobs’s NeXTSTEP software, which he developed after he left Apple in 1985. Upon his return to Apple in 1997, Apple bought NeXTSTEP, and its advanced software technology and human talent became a big asset to the company.
In Mac OS X 10.5, most .plist files are binary instead of being just regular text files; therefore, they cannot be opened correctly with the default TextEdit program.