There are different definitions of science, but basically science is the branch of study which seeks to observe, discover, and understand how the universe and everything in it works. Science is based on the scientific method, which is a systematized attempt to learn through observations, hypothesis, testing to validate or invalidate the hypothesis, and developing a theory (a principle generally accepted to be a true) that sufficiently explains the phenomena.
The word, “science,” comes from the Latin scientia which means “knowledge." There are different fields of science. There are physical sciences (physics, space, chemistry, etc.,), earth sciences (atmospheric, paleontology, geology, oceanography, etc.,), life sciences (evolution, ecology, neuroscience, etc.,), medical sciences (pharmacology, clinical research, aging, etc.,), social sciences (anthropology, archaeology, psychology, etc.).
Science has been successfully used to increase the quality of human life as well as our understanding of nature. The science of medicine, for example, researches human anatomy, how to repair it, and how to prolong life. Science has increased our knowledge of weather, planets, stars, and galaxies. It has helped us understand human behavior and aided us in increasing food production. It has helped us vanquish superstitions and foolish speculations and has given us radio, TV, cell phones, planes, and computers. It has served mankind well.
But science is insatiable. It is never satisfied with just knowing how or why something works. Science, or I should say scientists, seek to expand their area of knowledge sometimes even beyond accepted theories. To this end, science is always progressing and increasing our knowledge.
In brief, science is discovering and explaining the unexpected.