I have a shapefile that currently uses meters as the measure for its coordinate system, but the map framework I wish to use expects decimal degrees. I'd like to reproject my shapefile to use decimal degrees, but I can't seem to figure out how to do so.
In ArcMap, I bring up the Project tool (ArcToolbox -> Data Management Tools -> Projections and Transformation -> Feature -> Project), and I select my desired projection (Projected Coordinate Systems -> Continental -> North America -> USA Contiguous Albers Equal Area Conic USGS.prj), but I'm not sure how to select my desired units at that point. If I click "Modify..." I can edit the Projected Coordinate System Properties, and I would expect "decimal degrees" to be an option in the "Linear Unit" dropdown, but it's not.
How may I go about choosing to reproject into decimal degrees?
Short answer: I wasn't understanding the difference between Geographic Coordinate Systems and Projected Coordinate Systems. A Projected system describes a flat surface, and so it doesn't make sense to describe it in terms of degrees; whereas a Geographic system uses a 3-dimensional spherical surface, so degrees are appropriate.
A system like the Google Maps, which uses the Web Mercator projection along with latitudes and longitudes, presumably must reproject lat/lng coordinates on the fly.
Thanks to @Brad Nesom for helping to elucidate me. I'm accepting his answer for being patient and helpful :-)