A RAR (.rar) file is a proprietary compressed container file, similar to a ZIP (.zip) file. It was created by Eugene Roshal, hence the name Roshal ARchive. Roshal also helped develop programs to utilize the format, including the popular, WinRAR™. While the ZIP format predates this format, the latter has advantages over ZIP compression.
Software creates RARs by adding one or more files to a container, giving the archive the extension, .rar. Like zipped archives, files can be stored in this state but cannot be used until they are extracted or decompressed. Software like WinRAR extracts the files to a folder of choice. While this may sound no different than zipped files, the format has some significant advantages.
Using software, one can break up very large files into “bite size” multi-part volumes, named automatically in sequential order. For example, .r01, .r02, .r03 and so on. Newer versions of WinRAR use part01.rar, part02.rar, part03.rar. Breaking the file into small parts makes it easier to send across a network. Once received, the user double-clicks the first volume in the archive (e.g. .r01 or part01.rar), and an installed program will extract the contents, recombining all volumes into the original, single file with its original extension.
In addition to its ability to handle large files, the RAR format has other advantages over the ZIP format. Among these, the files compress more efficiently, resulting in smaller file sizes than zipped files, (though it takes slightly longer to compress and decompress these files). RAR files also incorporate redundancy or a "recovery record" stored within the archive, making it possible to repair a container that has been corrupted. Newer versions of the format also support Advanced Encryption Standard (AES) and multi-threading.
While WinRAR shareware is probably the best known program, the ability to handle these files has been licensed to many software developers. Current versions of Windows operating systems incorporate native support for ZIP files only, leading many users to use dedicated third-party compression programs for the extra features they provide and the ability to handle all types of files. One popular, free and open source compression utility is 7-zip, which handles RAR, ZIP, CAB, TAR and DEB formats among others.