iso The archive file format known as ISO is a disk image format. It is the popular archiving technology used to archive the contents of every sector of an optical disc or file system. Compatible disk imaging software is often required to author ISO images from an optical disk or file directory. Reading ISO images can then be done with the same disk imaging software either by directly opening the image file or by mounting the image file onto a virtual disk drive typically created by the imaging software. Archived ISO files can be easily distributed on today's high speed internetworks without limitation or as self-contained files via portable hard drives.
tgz The .gz filename extension refers to the GZIP file format and compression/decompression utility of the same name which was initially released in 1992. It is the extension given to files compressed using the gzip utility. Unlike other compression tools of the time, gzip was originally intended to be used as a tool to compress a single file as opposed to multiple files or entire directories compressed as a single archive. As a work around, multiple files can be archived using the TAR archive file format, then that single TAR archive would then be compressed using the GZIP format. This would give the file a filename extension of .tar.gz.