What a shell script comportment

An another question from a junior.
When we create a shell script, what extension (with ksh ) do we use.
And how can this file be use by the system to interprete the program.
Do we have to compile a ksh script file?

Unlike that "other" operating system, Unix does not require you to use specific extensions for your executable files. You can turn on the executable bit for any file by issuing the command "chmod +x filename"

shell scripts are interpreted, not compiled.