All living things require a source of energy, nutrients, water, space to grow and reproduce, and a relatively stable environment that allows homeostasis. Many organisms also require oxygen, but this is not a universal requirement, and oxygen is actually deadly to certain organisms. Indeed, beyond these basic categories of needs, the requirements of organisms vary vastly from species to species.
Living things all require energy, and they obtain that energy through one of three basic ways. The basis for almost all life is in photosynthesis, the use of energy in sunlight to create carbohydrates from oxygen and water. Thus, the sun is the basic source of energy for almost every organism. The only exception are certain specialist microbes that feed on inorganic chemicals near hydrothermal vents and similar extreme environments. These two categories are known as autotrophs or primary producers, and all other organisms gain their energy from feeding on them or on the organisms that eat them.
While the primary constituents of organisms are carbon compounds, every organism also requires other chemicals to form their cellular machinery, and must obtain these nutrient from their environments. Water is a major constituent of every form of life, and while certain organisms can survive dessication, they are universally inert while doing so.