The current "Storage & iCloud Usage" option within the iPhone's settings will be renamed "iPhone Storage" in iOS 11. (Presumably, if you're working on an iPad, it will be called "iPad Storage.) Within that menu is an innocuous-looking option called "Offload Unused Apps," with an Enable option. Apple's menu description says, "Automatically offload unused apps when you're low on storage. Your documents & data will be saved."
What's more, it appears you can choose individual apps to offload if you don't want to depend on Apple to automatically manage the process for you. Choosing the "Offload App" option for an individual app does the following, according to Apple: "This will free up storage used by the app, but keep its documents and data. Reinstalling the app will place back your data if the app is still available in the App Store."
It's worth noting that many apps, such as Google Drive, Facebook and Twitter, already store data in the cloud, so it's easy to delete and reinstall them as needed. But for any apps that you must keep to avoid losing data (such as games), offloading could be just what people with storage issues are looking for. Indeed, this feature could entirely break us of the habit of keeping apps around just in case we need them one day.