Benefits are the "buy now" decision-makers for your audience. When people hear or see the benefits, they'll make a subconscious decision on just how valuable that benefit will be to them. If the beneficial value is high enough, they will buy!
Following on from the previous step, an example benefit for our password keychain might be: "you can choose a different, more secure password for every website you use, without having to remember them all."
Expand on the list of all of your app's features, by writing the benefits each feature provides.