What is the difference between script and compile module?

Test script contains the executable file in WinRunner while Compiled Module is used to store reusable functions. Complied modules are not executable.
WinRunner performs a pre-compilation automatically when it saves a module assigned a property value of Compiled Module.
By default, modules containing TSL code have a property value of "main". Main modules are called for execution from within other modules. Main modules are dynamically compiled into machine code only when WinRunner recognizes a "call" statement. Example of a call for the "app_init" script:
call cso_init();
call( "C:\\MyAppFolder\\" & "app_init" );
Compiled modules are loaded into memory to be referenced from TSL code in any module. Example of a load statement:
reload (C:\\MyAppFolder\\" & "flt_lib");
or load ("C:\\MyAppFolder\\" & "flt_lib");