Google recently rolled outaffording Web and app developers the ability to have users sign in with Google credentials. Once an app is integrated with Google sign-in, data from the app can then be shared to Google+ much like sharing data with Facebook has occurred for a while now.
In order for the apps on your Android device to be compatible with the new system, an update to Google Play Services is required. There's nothing you need to do for the update to happen, it all takes place in the background and normally you wouldn't notice a thing. But this update also adds a new app icon to your Android device. The icon is for an app called Google Settings. The app really isn't an app, but more of a collection of shortcuts to the various settings screens for you Google account.
Launching the app will provide shortcuts to your Google+ settings, Maps & Latitude, Location, Search, and Ads. All of the options I just mentioned are already accessible on the device through different methods, but the Apps with Google+ Sign-In option is new. This setting allows you to manage the apps you've used to sign in and allowed to share information with your Google+ account. Tapping on an app listed will revoke its access.
If the icon hasn't shown up on your device yet, it's rolling out over the next few days and will eventually work its way to your app drawer. Or as Lifehacker pointed out, clearing Google Play Services data in Settings > Apps and restart your device to force the update.