In simple terms mental health is a person's "Emotional and psychological health".
It is a state of well being where a person feels happy, content and can cope with the normal day to day stress while believing in their own capabilities as well others.
A person with good mental health will be able to cope with life, play their part in their family, community and workplace and make the most of their potential. Mental health is as important as physical health throughout our life. A person's mental health does not always stay positive, it can change with times, depending on what you are going through in your life and circumstances.