"Life" distinguishes the fundamental and functional being from the dead. It's a state characterized by ability to metabolize and grow, react to stimuli, and to reproduce. A baseball is an inanimate object incapable of growth, void of metabolic processes, and therefore incapable of life. The dog fetching the baseball in his mouth is capable of all of the aforementioned characteristics, and is therefore alive, the term used for those who have "life."
Life is also the physical and mental experiences that make up the existence of an individual, one or more aspects of the process of living. Today my "life" consisted of talking politics at lunch with friends, working, and sleeping.
Life, the meaning of it and it's essence has been studied, and written about for ages. The purpose of life has been questioned for centuries. From Greek philosophers such as Plato and Aristotle, to global strategist theologians like Rick Warren, author of The Purpose Driven Life.