GDFN is the Greater Detroit FreeNet. The definitions of some other acronyms that are commonly seen online may be found in Appendix A . These files are either compressed, archives, or both. You will need a program to extract the file or files from them. An archive is a set of files combined into one file.
Compression is a way to make the same data take up less space.
But .tar files are just archives, which aren't compressed, and .Z and .gz files are single compressed files. You can also have compressed tar files, known as .tar. A list of some common archive formats can be found in Appendix B .