In project management, functional requirements and non-functional requirements both constitutes solution requirements. Solution requirements describe features, functions, and characteristics of the product, service, or result that will meet the business and stakeholder requirements.
Functional requirements : describe the behaviors of the product. Examples include processes, data, and interaction with the product.
Non-Functional requirements : supplement function requirements and describe the environmental conditions or qualities required for the product to be effective. Examples include reliability, security, performance, safety, level of service, supportability, retention/purge.