Compressed Files Extensions - What are compressed files and how do I open a compressed file?

What are compressed files and how do I open a compressed file?

File Type Category File Format
.7z Compressed Files 7-Zip Compressed File
.ace Compressed Files WinAce Compressed File
.ar Compressed Files Unix Static Library
.b1 Compressed Files B1 Compressed Archive
.bmz Compressed Files Portal Bonus Map Zip File
.bz2 Compressed Files Bzip2 Compressed File
.bzip Compressed Files Bzip Compressed Archive
.cpgz Compressed Files Compressed CPIO Archive
.gpk Compressed Files WaveLab Audio Peak File
.gz Compressed Files Gnu Zipped Archive
.ipg Compressed Files iPod Game File
.lzma Compressed Files LZMA Compressed File
.mtz Compressed Files MIUI Theme
.par2 Compressed Files Parchive 2 Index File
.r00 Compressed Files WinRAR Compressed Archive
.rar Compressed Files WinRAR Compressed Archive
.s7z Compressed Files Mac OS X 7-Zip File
.sfx Compressed Files Windows Self-Extracting Archive
.z01 Compressed Files WinZip First Split Zip File
.zi Compressed Files Renamed Zip File
.zip Compressed Files Zipped File
.zipx Compressed Files Extended Zip File
.zix Compressed Files WinZix Compressed File
.zoo Compressed Files Zoo Compressed File