A chronotype is an individual's natural predisposition toward earlier or later sleep-wake timing, commonly bucketed into three types: 'owls' (evening-preferring), 'larks' (morning-preferring), and intermediate types (the majority of the population). Chronotype is treated as a real, biologically-grounded individual difference — not just a preference — and is presented as worth designing schedules around, e.g., avoiding demanding meetings or decisions before 11 AM for evening-leaning individuals or teams.
Caveat: popular self-labeling as an 'owl' or 'lark' (e.g., via online quizzes) may not reliably capture true circadian phenotype; the validity of casual self-assessment is uncertain.
Related: Delayed School Start Times and Adolescent Circadian Shift describes an analogous population-level circadian shift (adolescents skewing later) with policy implications.
Beyond identifying which type you lean toward (evening owl, morning lark, or an intermediate profile), the practical takeaway is to arrange commitments around that tendency where possible — e.g., a night owl avoiding early-morning meetings or workouts — rather than forcing a schedule that fights the underlying chronotype.