Another name for the greater than ( > ) symbol when referring to a command in a command line environment such as MS-DOS or Linux. For example, in the example below the append symbol is between the command and the output file that stores the output.
dir > dirout.txt
In the above example, instead of outputting the results of the dir command to the screen all output would be stored in the dirout.txt file. In Linux you can replace the dir command with the ls command to achieve the same results.
echo this is an example >> test.txt
In the next example, this command would append "this is an example" to the end of the test.txt file using echo.