What is the use of aura:set in Lightning Component in Salesforce?

<aura:set>: this lightning component is used in markup to set the value of an attribute inherited from a component or event. e.g.:
<div><div><aura:component>

<div><div> <ui:button label=”Save”>

<div><div> <aura:set attribute=”buttonTitle” value=”Click” to=” save=”” the=”” record=””></aura:set>

<div><div> </ui:button>

<div><div></aura:component>

</div></div></div></div></div></div></div></div></div></div>