Underscore using within functions

Certified Senior Developer

Hi,

In some ER code, I have found this kind of things :

rule!APP_GreaterTo(value: _, to: 14),

or :
      contains(
        reject(
          isnull(_),
          ri!names
        ),
        tostring(ri!name)
      ),                                                 
Could you explain me what does mean that "_" ?
is it just to specify we do not want to pass any parameter in the function ?  (because "isnull()" is not authorized)
but why "value: _"  in place of "value: null" ?

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