私人 (sī rén) as an attributive noun means 'private, personal' — it describes something belonging to or concerning an individual (e.g., 私人财产, 私人空间). It differs from 个人 (gè rén 'individual, personal'), which is more about the individual's own opinion or perspective (e.g., 个人看法). 私人 also has a second sense as a noun meaning 'a close associate, confidant' (e.g., 老板的私人).