Stress levels refer to the intensity or severity of stress that an individual is experiencing. It can be measured through various methods, such as self-report surveys, physiological measures like heart rate variability, and objective indicators like changes in behavior or performance. Stress levels vary from person to person and can also change over time depending on the circumstances and experiences of each individual. High stress levels can have negative effects on mental and physical health, while managing stress effectively can help improve overall well-being.