Stakeholder needs vs requirements: the CAPM distinction
A need says what a stakeholder needs the system to do, from the outside. A requirement says what the system must do to meet that need, from the developer's side. Needs are broad and stable; requirements and user stories are narrower and are written from the needs.
User needs
GOV.UK defines user needs as the needs a user has of a service, which the service must satisfy for the user to get the right outcome. They are usually written as 'I need/want/expect to... so that...', from a personal perspective in words users would use.
Good user needs sound like something a real user might say, are based on research evidence rather than assumptions, and focus on the user's problem, not a solution: needing a reminder, not needing an email or letter. Treat opinions that do not come from users as assumptions to be proven by research.
User needs tend to be high-level, broad in scope and stable over time. User stories are written from them in a more constrained format, with acceptance criteria, complexity and dependencies. Keep track of which need each story relates to; this traceability shows how well a need is being met.
Needs and requirements in systems engineering
SEBoK says needs give the stakeholders' expectations of the system from an external, black-box view. Requirements give the technical, developer view of what the system must do to meet those needs, from an internal, white-box view.
Stakeholder needs are combined with drivers and constraints, risks and life cycle concepts into an integrated set of needs. System Requirements Definition then transforms that set into design-input requirements. One need can produce several requirements.
Where the exam catches people
Believing a user need can name a solution such as an app or email: good needs describe the problem, not the solution.
Believing user needs change every sprint: GOV.UK says they tend to be broad and stable over time, while stories are more specific.
Believing a senior manager's view of what users want is a user need: unsupported opinions are assumptions to be proven by research.
Believing needs and requirements are the same view: needs are the stakeholder's black-box view, requirements the developer's white-box view.