Users moves from aggregate to individual.
Profiles
A profile shows one person's history: what they did, in order, with properties.
Why it is useful
Aggregates tell you something is wrong; individuals tell you what. A funnel drop becomes obvious when you watch three people hit the same obstacle.
Finding someone
Search by identifier, or arrive from a report by drilling into a segment.
Privacy
Profiles contain behavioural data about identifiable people. Access follows your workspace permissions, and you should apply the same care here as anywhere else holding personal data.