Cement is a basic Python command-line application framework. Almost every command line type application has a number of basic pieces that have to exist before any real code and logic gets written. At a minimum, Cement easily sets up the following: Configuration file parsing, Command line arguments and option parsing, Logging, and Plugin support.
These four pieces are the most important for a fully functional command line application. Normally to accomplish what's listed above would require dozens of lines of non-reusable code for every application before you even begin coding. Cement doesn't re-invent the wheel, rather uses OptParse, ConfigObj, and Logger behind a number of methods that wrap them all together nicely. With Cement, the above pieces of a fully functional command line application are configured with more or less a single line of code.
Cement is most generally used as a starting point from which to begin developing a command line type application. That said, applications using cement can also share plugins with either cement or other applications using cement.
Cement adds two commands to PasteScript that can be used to easily create cement based applications and plugins. See 'paster cement-app' and 'paster cement-plugin'.