<aura:component controller="ContactListController">

    <aura:attribute name="contacts" type="Contact[]"/>
    <aura:handler name="init" value="{!this}" action="{!c.doInit}" />
    <aura:iteration items="{!v.contacts}" var="contact">
        <p>{!contact.Name}</p>
        <p>{!contact.Phone}</p>
    </aura:iteration>
</aura:component>

({
    doInit : function(component, event) {
        var action = component.get("c.findAll");
        action.setCallback(this, function(a) {
            component.set("v.contacts", a.getReturnValue());
        });
        $A.enqueueAction(action);
    }

public with sharing class ContactListController {
    public static List<Contact> findAll() {
        return [SELECT id, name, phone FROM Contact LIMIT 50];
    }
}

public with sharing class ContactListController {
   @AuraEnabled
  public static List<Contact> findAll() {
    return [SELECT id, name, phone FROM Contact LIMIT 50];}}

function(components, status, errorMessage){
                if (status === "SUCCESS") {

                    //DO SOMETHING
                }
                else if (status === "INCOMPLETE") {
                    console.log("No response from server or client is offline.")
                    // Show offline error
                }
                else if (status === "ERROR") {
                    console.log("Error: " + errorMessage);
                    // Show error message
                }