Product Requirements

Summarized as Product Requirement Document (PRD)

Describes how system needs to operate to meet the business and user requirements

Listed as User stories i.e. short, one-sentence description of features from user's PoV

As a < role/persona >
I want to < activity >
So that I can < outcome > 

To evaluate user stories, use the INVEST criteria

• Independent: easily prioritized in planning
• Negotiable: Not a contract
• Valuable: measure outcome & impact
• Estimatable: must be sizable
• Small : Keep scope small
• Testable : devs should be able to validate

User stories are classified as functional and non-functional requirements.