A ".tar" file is an archive format commonly used in Unix-based operating systems. It combines multiple files into a single file, preserving their directory structure. The ".tar" extension stands for "tape archive." These files are often compressed using additional algorithms like gzip or bzip2, resulting in ".tar.gz" or ".tar.bz2" extensions. The "file.tar" is likely a specific example of a ".tar" file, representing a collection of files and directories bundled together.