The concept of a map projection isn't difficult to grasp- it's something students in an undergraduate introductory geography class learn as a matter of course. It's the basic procedure of taking the 3-dimensional, (roughly) spherical surface of the earth, and transcribing it to a 2-dimensional surface to make a map. In practice, though, there are a myriad of ways this can be done, and all produce results that differ in a myriad of different respects. To put it simply, different maps, layered together in GIS, will not line up exactly in most cases if they have differing map projections. The kinds of basic GIS functions I've used in jobs I've held thus far haven't necessitated learning much about how this works within the GIS, and it's been a topic I've long felt both a fear of not understanding, and a trepidation about attempting to learn, lest it be beyond my comprehension.
With the creation of the above I can say I finally understand exactly how map projections work both conceptually, and within the use of a GIS. The three different maps of Florida are all done with different map projections, and the difference in area each gives for the 4 selected counties is listed below. Going through the steps of using GIS to re-project these maps as required, and exploring the inherent spatial differences in each, has (finally) illuminated, for me, the arcane knowledge of the map projection. Yes, it is somewhat complicated; no, it isn't beyond my ability to comprehend. I only wish I would've realized this sooner, but I suppose there is a time and place for everything- the truth in which is evident in really any well made map.
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