This template accepts up to 6 licenses (the first 6 unnamed parameters, which should be the names of image license templates), and displays them as options to choose between in a multi-license. If the image was not uploaded by its author, you can change "I" at the start of the template to another name by setting the author= parameter.
The optional migration= parameter corresponds to keywords in the {{license migration}} template series and is used to track the license update process for GFDL images.
Here are 3 examples of multi-license templates along with links to their component parts: