Chronological age is the amount of time a person has been alive, while real age takes into account factors like health and lifestyle choices that can affect how "old" a person feels.
For example, someone who is chronologically 50 years old but has the health of a 30-year-old would have a real age of 30.
Chronological age is the most common way to measure age, but real age can accurately predict a person's health and longevity.