tar The .tar filename was originally designed to be used as a TApe ARchiver to store entire file systems and files as single files on tape storage medium. It was designed by AT&T in 1979. Today, the format more commonly refers to an archive or collation of multiple files into a single file with the .tar filename extension. The format is an open source file archive format commonly associated with the UNIX tar command however other data compression tools are capable of effectively compressing and/or decompressing files saved with the .tar file format. Doing so typically adds the compression filename extension to the archive file for example .tar.bz2.
jar A .jar extension file is a Java Archive format file that is used to store a large number of files into one single file. The basic advantages of .jar extension files are data compression, archiving, decompression, unpacking of the archived file and electronic signing which is one of the advanced features of this format. The Java Development Kit (JDK) contains the Java Archive Tool that is used to perform the basic tasks on .jar extension files. The JAR format is similar to a ZIP file format and it was specifically developed to help download Java applets and its components that include class files, images and sounds in one single HTTP transaction.