concept feature card in category agile

This is an excerpt from Manning's book Becoming Agile ...in an imperfect world.
Agile processes improve prioritization and deliver higher-value features first. This is accomplished by creating feature cards or user stories and evaluating features before requirements are detailed. You’ll evaluate features for their customer value, level of risk, frequency of use, and dependencies. This allows you to do the following:
Feature cards are similar to the user stories used in Extreme Programming (XP) development. We also often use the term feature shell to describe a feature card. The card provides enough information to plan a feature and discuss it quickly. The size of the card also makes it easy to track a feature and re-plan when necessary.