Lightning Component :

An component can be created multiple times in an app or in another component. This is called instantiation of an component

The markup present in an component is called component definition

This is similar to class definition and object creation in java

The following programs shows a demo of attribute usage in lightning

component:

Create a lightning component with the below markup code
Name the component as helloWorld

<!--


 * created by 		:		Shiva RV
 * Date				:		14-10-2018
 * Description		:		Attribute and Action Usage in lightning
  
-->

<aura:component >
    
    <!-- start of Attribute declaration -->
     <aura:attribute type="String" name="message" default="hello default Message"></aura:attribute>
    <!-- Register Event -->
	
    <!-- End Of Register Event -->
    
    Hello String Attribute Data --- {!v.message} 
   
</aura:component>

Below is the hello world App code:
<!--


 * created by 		:		Shiva RV
 * Date				:		13-10-2018
 * Description		:		Hello World Lighting App
  
-->

<aura:application extends="force:slds">
    
    <!-- Multiple Instance of Component With Attribute Change -->
    <c:DemoCompForMultipleInstance message="Hello Buddy"></c:DemoCompForMultipleInstance>
  	<br/>
    <c:DemoCompForMultipleInstance message="Nice To See You"></c:DemoCompForMultipleInstance>
     <br/>
    <c:DemoCompForMultipleInstance ></c:DemoCompForMultipleInstance>
    
</aura:application>
Output:

Key Notes :
*You can see multiple instance of same component with different parameter in this app demo