Every single update made to your app or to how your app is displayed in the app stores must go through the approval process. This can take up to 2 weeks at times (but is generally quicker!).
You won't be able to make other updates while your app is undergoing approval; however, you can update again once approved. It's best to make numerous changes at once for fastest effect.
The current version of your app will stay operational until the new version is approved.