Salesforce Lightning Data Service Demo Code

AccountEdit.cmp.html

<aura:component implements="force:appHostable,
flexipage:availableForRecordHome,force:hasRecordId" 
access="global" >

	<aura:attribute name="account" type="Object" 
	  description="The record object to be displayed"/>
	<aura:attribute name="accountRecord" type="Object" 
	  description="A simplified view record object to be displayed"/>
	<aura:attribute name="recordSaveError" type="String" 
	  description="An error message bound to force:recordData"/>
    
    <force:recordData aura:id="accRec" 
        layoutType="FULL" 
		recordId="{!v.recordId}"  
		targetError="{!v.recordSaveError}"
		targetRecord="{!v.account}"
		targetFields="{!v.accountRecord}"
		mode="EDIT"
		 recordUpdated="{!c.recordUpdated}"/>
    
     <div class="slds-box"> 
        <div class="slds-text-heading_medium">
            Edit Account - Data Service
        </div> 
        <div class="slds-form--stacked slds-tile"> 
            <div class="slds-form-element">
                <label class="slds-form-element__label"  >Name: </label>
                <div class="slds-form-element__control">
               		<ui:inputText aura:id="recordName"  class="slds-input"  
                                value="{!v.accountRecord.Name}"
                                required="true"/>
                </div>
            </div>
             <div class="slds-form-element">
                 <label class="slds-form-element__label"  >Company Email: </label>
                 <div class="slds-form-element__control">
               		<ui:inputText aura:id="companyEmail"  class="slds-input"  
                                value="{!v.accountRecord.Company_Email__c}"
                                required="true"/>
                 </div>
            </div>
            <div class="slds-form-element">
               <ui:button aura:id="saveAccount" 
                buttonTitle="Save Account" class="button" label="Save Account" press="{!c.saveAccount}"/>
            </div>
        </div>
        
           <aura:if isTrue="{!not(empty(v.recordSaveError))}">
               <br />
            <div class="error slds-box">
                 {!v.recordSaveError}
            </div> 
        </aura:if>
    </div>
</aura:component>

AccountEdit.css

.THIS .error {
    background-color: #c23934;
        border: 1px solid #c23934 ;
        color: white;
}

AccountEditController.js

({
	saveAccount : function(component, event, helper) {
		 helper.saveAccount(component, event, helper);
	},
    recordUpdated : function(component, event, helper) {
		 helper.recordUpdated(component, event, helper);
	}
})

AccountEditHelper.js

({
	saveAccount : function(component, event, helper) {
		component.find("accRec").saveRecord($A.getCallback(function(saveResult) {
            if (saveResult.state === "SUCCESS" || saveResult.state === "DRAFT") {
                console.log("Save completed successfully.");
            } else if (saveResult.state === "INCOMPLETE") {
                component.set("v.recordSaveError","User is offline, device doesn't support drafts.");
            } else if (saveResult.state === "ERROR") { 
                var errMsg = "";
                // saveResult.error is an array of errors, 
                // so collect all errors into one message
                for (var i = 0; i < saveResult.error.length; i++) {
                    errMsg += saveResult.error[i].message + "\n";
                }
                component.set("v.recordSaveError", errMsg);
                
            } else {
                component.set("v.recordSaveError",'Unknown problem, state: ' + saveResult.state + ', error: ' + 
			      JSON.stringify(saveResult.error));
            }
        }));
	},
    recordUpdated : function(component, event, helper){
        var changeType = event.getParams().changeType;
		if (changeType === "CHANGED") {
            component.find("accRec").reloadRecord();
        }
    }
})

recordUpdated="{!c.recordUpdated}" What is the use of this attribute ? When does it fire the controller function?