Generally, a script is a program that is not compiled. Rather, it is fed through an interpreter, which then executes the instructions in the script and performs the required actions.
A script, such as a shell script, is useful for performing long tasks that you have to do often. Just make a script and then run it whenever you want to perform the task. A shell script contains a list of commands to execute to perform a task.
A perl script can be like a shell script, but it can also be used on web sites for producing dynamic content, such as web forums.