A ".tar" file is a type of archive file used in Unix and Linux systems. The name stands for "tape archive," and it is designed to combine multiple files and directories into a single file for easier storage and transfer. Unlike compression formats, a .tar file does not reduce the size of the files; it simply packages them together. To create a .tar file, users typically use the command line with the command "tar -cvf" followed by the desired filename and the files to include. To extract files from a .tar archive, the command "tar -xvf" is used. This format is often used in conjunction with compression methods like gzip or bzip2 to create compressed files with extensions like ".tar.gz" or ".tar.bz2."