Batch files are short mini programs created to accomplish repetitive tasks easily. A batch file is a text file with a file extension of BAT. Batch files contain short scripts with a sequence of commands for a Windows operating system. The commands are run in the order that they are listed. This "batch" or series of commands, is written as one file, thus avoiding the process of entering these commands individually from the keyboard.
You, as the computer user, can write your own batch file. By writing the commands, in the correct computer "lingo", you can avoid manually entering repetitive commands and have the computer do that for you.
A note of caution though. Batch files are program files and should only be run if you trust the source of the file.
For more information on batch files, see What is a BAT File?.