According to Wikipedia, Independence is a high-fidelity replica of the space shuttle. The timing of its construction would seem to be post-Challenger, but before Columbia and the subsequent winding down of the program. What motivated the construction of such a thing at that point in time? Was it built solely as a full-scale display model, or did it have utility in the shuttle program as a mock-up?
It was built solely for display at KSC's visitor center, as described in the Wikipedia article you reference, and in this article about Orbiter mockups.
Explorer was built primarily for display and educational purposes--visitors could actually go inside the replica to tour the payload bay and crew cabin.
(Explorer was renamed Independence after its move to Houston. Other, sarcastic, names suggested by JSC employees such as Fauxlumbia/Ainterprise/Notlantis weren't accepted...)