By "assuring" their project a client promises to award a winner no matter what. This means that they waive their ability to get a refund. Since the creatives know a winner is guaranteed to be chosen, projects with Client Assured awards typically attract more participation and consequently receive more entries.
Assuring your award is an option you can select right as you post your project. It will look like this:
You can also assure your project after it has posted by going to the Settings tab in your project (as shown below):
And, then click the box next to "Assure your awards" on the right side of the screen. It's as easy as that!
Creatives can easily see if your project is assured when browsing through Explore.