Purpose is defined as a sense of knowing that your life has meaning, importance, and value. Living and knowing your purpose in life mean that you believe your life, your work, and your contribution (will) make a positive impact on the life of others. Living with purpose means you are committed to serving society in a positive way.
A life with a purpose (and passion) is a life well-lived. Take David Davey for example. Dave, then 12-years-old, was struck with polio during the epidemic of the 1940s. (At the time, polio was known by the dread name of Infantile Paralysis.) He was fortunate he survived but the disease took away the strength of his legs. He was confined to the wheelchair for the rest of his life.