What is a GeoTIFF and what is it used for?

GeoTIFF is a non-proprietary geographic TIFF file format. The purpose
of GeoTIFF is to provide information that lets raster imagery (scanned
maps, satellite images, results of geographic analysis, etc) be read
automatically into correct position and scale within many GIS
softwares. GeoTIFF implements a tag structure which embeds the
geographic information methodically and interoperably (and invisibly to
most users) inside the TIFF file.