It's purely for Intellisense. However, I have seen times when a VFP COM object could not be consumed if the type of a parameter was not specified. So, this would not work

DEFINE CLASS Example AS Session OLEPUBLIC
    FUNCTION DoSomething(tnParam1, tcParam2)
        * Do some processing
    ENDFUNC
ENDDEFINE

But this would

DEFINE CLASS Example AS Session OLEPUBLIC
    FUNCTION DoSomething(tnParam1 AS Integer, tcParam2 AS String)
        * Do some processing
    ENDFUNC
ENDDEFINE

>I have seen references in code that look like this:

Local lnSomething as Integer

>Obviously this tells me that {lnSomething} is an integer, but I knew that because it begins with ln,
>
>So, what is the purpose in doing so? Does VFP use this information in some way?
>
>P.S.: I do understand the use of this structure when it refers to 'as Form', or whatever, just not when it refers to a datatype like String or Integer.