Age of Imperialism is a modification for EU2 that enhances the game in different ways. It expands the time period by almost 200 years so that it runs from 1337-1913 instead of the standard 1419-1820. The scenario makes use of many of the events and edits of the Age of Nationalism (Europa Universalis II) mod.
It furthermore adds several new scenarios as well as new countries, events (and changes many standard EU2 events, drastically in some cases), leaders and monarchs. On top of that, it comes with unique new graphics. It also contains lots of minor tweaks and additions to the database files.