Doesn't actually describe in the intro what the fallback actually does

[lauracowen]

In the "What you'll learn" and "Getting Started" sections, the text alludes to:

• "fallbacks offer an alternative result when an execution does not complete successfully."
• "You will add fault tolerance to the inventory service so that it reacts accordingly when the system service is unavailable."
• "to define criteria for when to provide an alternative solution for a failed execution."
• "The fallback mechanism is triggered because the system service is now in maintenance. You see the cached properties for this localhost."

This last point does at least say what the fallback solution looks like but none of them say what's happening, what the fallback mechanism does (in one sentence or less). I'm assuming it accesses the stored text in the Inventory service if it can't access the System service but that's never actually stated.