Life is the aspect of existence that processes, acts, reacts, evaluates, and evolves through growth (reproduction and metabolism). The crucial difference between life and non-life (or non-living things) is that life uses energy for physical and conscious development. Life is anything that grows and eventually dies, i.e., ceases to proliferate and be cognizant. Can we say that viruses, for example, are cognizant? Yes, insofar as they react to stimuli; but they are alive essentially because they reproduce and grow. Computers are non-living because even though they can cognize, they do not develop biologically (grow), and cannot produce offspring. It is not cognition that determines life, then: it is rather proliferation and maturation towards a state of death; and death occurs only to living substances.
Or is the question, ‘What is the meaning (purpose) of life?’ That’s a real tough one. But I think that the meaning of life is the ideals we impose upon it, what we demand of it. I’ve come to reaffirm my Boy Scout motto, give or take a few words, that the meaning of life is to: Do good, Be Good, but also to Receive Good. The foggy term in this advice, of course, is ‘good’; but I leave that to the intuitive powers that we all share.