“GDAL is a translator library for raster geospatial data formats that is released under an X/MIT style Open Source license by the Open Source Geospatial Foundation. As a library, it presents a single abstract data model to the calling application for all supported formats. It also comes with a variety of useful commandline utilities for data translation and processing.”
A fairly good and comprehensive intorduction to GDAL can be found here.
The webiste a bit Linux focused but also relevant for other operating systems when using the gdal library.
Fore GeoTIFF file creation with GDAL check: