How we can use aura:method to call child JS Controller in Salesforce?

<aura:method> enables you to directly call a method in a component’s client-side controller instead of firing and handling a component event. Using <aura:method> simplifies the code needed for a parent component to call a method on a child component that it contains.
e.g , how to define parameters in aura:method.
<aura:method name="sampleMethod" action="{!c.doAction}"
description="Sample method with parameters">
<aura:attribute name="param1" type="String" default="parameter 1"/>
<aura:attribute name="param2" type="Object" />
</aura:method>