What is the difference between this extension and the charinsert gadget? Do I need to install both or only one of them to get the the drop-down box like wikipedia?
Topic on Extension talk:CharInsert/Archive 2
To get the drop-down box, you need Extension:Gadgets, too. See instructions at Extension:CharInsert#Advanced_Installation.
What does this extension provide that the gadget doesn't?
I've deployed the gadget, and removed this extension, and I get all the features that I required. It seems this extension is only required if one doesn't want to deploy the gadgets extension.