FileInfo.com - The File Extensions Resource

.GZIP File Extension

File Type	Gnu Zipped File
File Format	File
Common?	No
File Description	Compressed archive created using the Gnu gzip compression algorithm; gzip (GNU Zip) is an open source compressor included with many Unix systems. More information is available at the gzip home page. Gnu zipped files also use the .GZ extension.
Program(s) that open gzip files	Mac: Smith Micro StuffIt Deluxe for Mac; Apple Archive Utility Windows: Smith Micro StuffIt Deluxe for Windows; Corel WinZip; 7-Zip Unix: Xarchiver; gunzip

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/gzip