Common Cartridge is a standard created by the by the IMS Global Learning Consortium that allows digital content and assessments to be bundled together in a package and then imported into a Learning Management System.
This is especially useful when using multiple LTI tools to assemble a course. For example, the course content could be created with CourseArc, quizzes with Quizlet, and a collaborative class notebook with OneNote Class Notebook. The cartridge can also be designed to include pre-configured assessments and discussion boards.
This information is represented in a series of XML files in versions 1.0 through 1.2 of Common Cartridge, and a single XML file in version 1.3. The common cartridge package can then be imported into any LMS that supports the standard.
To find out more about the current Common Cartridge specification, read the 1.3 specification here.