An "immune booster" typically refers to a substance or practice that is believed to enhance the body's immune response, helping to defend against illnesses and infections. These can include various vitamins, minerals, herbs, and lifestyle practices such as proper nutrition, regular exercise, stress management, and adequate sleep. While some immune-boosting supplements and practices may have supportive evidence, it's essential to approach claims with caution and consult with a healthcare professional before making significant changes to your health regimen.