IMS is a body which helps define technical standards for various things, including e-learning material. The IMS Content Packaging specification makes it possible to store chunks of material in a standard format which can be re-used in different systems, without having to convert the material into new formats.
The IMS content package in Moodle enables such content packages to be uploaded and included in Moodle courses. There are various options for displaying content in a pop-up window, with a navigation menu or buttons etc.