The firebase-app element is used for initializing and configuring your connection to firebase.
firebase-auth is a wrapper around the Firebase authentication API. It notifies
successful authentication, provides user information, and handles different
types of authentication including anonymous, email / password, and several OAuth
workflows.
Example Usage:
<firebase-app
  auth-domain="polymerfire-test.firebaseapp.com"
  database-url="https://polymerfire-test.firebaseio.com/"
  api-key="AIzaSyDTP-eiQezleFsV2WddFBAhF_WEzx_8v_g"
  storage-bucket="polymerfire-test.appspot.com"
  messaging-sender-id="544817973908"
  project-id="polymerfire-test">
</firebase-app>
<firebase-auth id="auth" user="{{user}}" provider="google" on-error="handleError">
</firebase-auth>The firebase-app element initializes app in firebase-auth (see
firebase-app documentation for more information), but an app name can simply
be specified at firebase-auth's app-name property instead.
JavaScript sign-in calls can then be made to the firebase-auth object to
attempt authentication, e.g.:
this.$.auth.signInWithPopup()
    .then(function(response) {// successful authentication response here})
    .catch(function(error) {// unsuccessful authentication response here});This popup sign-in will then attempt to sign in using Google as an OAuth
provider since there was no provider argument specified and since "google" was
defined as the default provider.
The firebase-document element is an easy way to interact with a firebase location as an object and expose it to the Polymer databinding system.
For example:
<firebase-document
  path="/users/{{userId}}/notes/{{noteId}}"
  data="{{noteData}}">
</firebase-document>This fetches the noteData object from the firebase location at
/users/${userId}/notes/${noteId} and exposes it to the Polymer
databinding system. Changes to noteData will likewise be, sent back up
and stored.
<firebase-document> needs some information about how to talk to Firebase.
Set this configuration by adding a <firebase-app> element anywhere in your
app.
firebase-query combines the given properties into query options that generate
a query, a request for a filtered, ordered, immutable set of Firebase data. The
results of this Firebase query are then synchronized into the data parameter.
Example usage:
<firebase-query
    id="query"
    app-name="notes"
    path="/notes/[[uid]]"
    data="{{data}}">
</firebase-query>
<template is="dom-repeat" items="{{data}}" as="note">
  <sticky-note note-data="{{note}}"></sticky-note>
</template>
<script>
Polymer({
  properties: {
    uid: String,
    data: {
      type: Object,
      observer: 'dataChanged'
    }
  },
  dataChanged: function (newData, oldData) {
    // do something when the query returns values
  }
});
</script>