An orthomosaic map is an up-to-date high resolution aerial map from the top down similar to what you would find using Google Maps or Google Earth, but with much higher resolution. Here is a map captured last year August 2020 of the clubhouse at the Brickyard Golf Club in Macon, GA.
An orthophoto, orthophotograph or orthoimage is an aerial photograph geometrically corrected (“orthorectified”) such that the scale is uniform: the photo has the same lack of distortion as a map. Unlike an uncorrected aerial photograph, an orthophotograph can be used to measure true distances, because it is an accurate representation of the Earth’s surface, having been adjusted for topographic relief, lens distortion, and camera tilt.