Definition:
Role-Feature-Reason is a template used by Product Owners, Team members and other stakeholders who is gathering requirement as User Stories .
Requirement written with this template describes the right objective from users perspective. This helps to understand the feature, how the actual user will utilise that feature, how he benefits.
As a [type of User] I want [some feature] so that [some reason]
The role (Who) The feature (what) The reason (why)
As a account holder, I want to check my balance online, so that I can do a purchase.
This template used in Agile Software Development helps to capture the requirement of a software feature. Helps the requirement to evolve and is supposed to aid in future conversation to pay attention not just to “what” the desired software product is to do, but also “from whom” it does matter and for “what objectives”
Further Reading:
Book: User Stories Applied: For Agile Software Development by Mike Cohn
https://www.agilealliance.org/glossary/role-feature/
http://codesqueeze.com/the-easy-way-to-writing-good-user-stories/