<override> tag in services.xml

[ThiepLV]

Hi all

can anyone tell me what mean <override> tag in services.xml?

For example:
  <service name="createPayGrade" engine="simple" default-entity-name="PayGrade"
             location="component://humanres/script/org/ofbiz/humanres/HumanResServices.xml" invoke="createPayGrade" auth="true">
        <description>Create a Pay Grade</description>
       
        <auto-attributes mode="INOUT" include="pk" optional="true"/>
        <auto-attributes mode="IN" include="nonpk" optional="true"/>
        <override name="payGradeName" optional="false"/>
    </service>

Thank a lot