"I want to be able to have a response time of X minutes for our technical team to resolve a customer problem."

In short, functional requirements are functional features that users expect from a proposed software product. Non-functional requirements, on the other hand, are more related to security, performance, and the look and feel of the user interface, a.k.a. (UI). For a project to be successful, it is critically essential that both the customer and the project delivery teams have a clear definition and agreement on what the project scope and detailed requirements are going to be.

There are three types of requirements: conscious, unconscious, and unidentified or TBD requirements.
When a hiring manager asks this question, they want to know if part of your job requires gathering and analyzing functional or non-functional requirements. For functional requirements gathering, they will want to hear how the system behaves under certain conditions within its environment, how it responds to inputs, and what outputs it generates. As far as non-functional requirements, they will want to also hear things like constraints on the system, quality attributes, security, performance, and availability.

"Yes, I work with cross-functional teams within our organization on functional and non-functional requirements. I take a unique approach to how I address these types of requirements. It's a step-by-step method, really. There are three requirement types that I use--conscious, unconscious, and unknown requirements. Consciousness is when stakeholders have a high-level awareness of the basic requirements. Unconscious is what stakeholders would like to see but didn't translate the message clearly enough to see the desired result. This stakeholder assumes that the work they envisioned will be delivered, which in most cases falls short of their expectation. Unknown is the type that has yet to be imagined or realized. Stakeholders typically don't give input into this type because they assume it is not achievable or cannot be delivered as expected."