If you own more than one iOS device, iCloud Tabs are a quick and easy way to pull up web pages you have open on another iPhone or iPad associated with your Apple ID. If you use them frequently, note that how you access them on iPhone has changed in iOS 7. Haven't figured it out yet? Here's how:
Launch the Safari app from the Home screen of your iPhone.
Tap on the new page icon in the lower right hand corner of the screen.
Here you can see all the pages you currently have open. Simply flick upwards and underneath all your open tabs you will see a list of all the open iCloud tabs from other devices. Just tap on the one you'd like to load.
That's all there is to it. We aren't sure why Apple decided to only move iCloud Tabs on the iPhone, let alone to such a hidden area that isn't very obvious. If you're using an iPad, just tap on the cloud icon by the address bar like you've always been able to do. This is a much more obvious design choice than the relocated iCloud Tabs section on iPhone.