In the context of iPhone development, Property Lists are a key-value store that your application can use to save and retrieve persistent data.
All iPhone applications have at least one of these by default, the Information Property List:
The information property list is a
file named Info.plist that is included
with every iPhone application project
created by Xcode. It is a property
list whose key-value pairs specify
essential runtime-configuration
information for the application. The
elements of the information property
list are organized in a hierarchy in
which each node is an entity such as
an array, dictionary, string, or other
scalar type.