Our sun provides the energy that powers all life on this planet. The nuclear hydrogen fusion reaction in the stellar core liberates heat and light that are emitted as photons that reach earth in eight minutes. This heat speeds up life generating chemical reactions allowing them to proceed at a reasonable rate. Photons from the sun are absorbed by chlorophyll in plants, powering the photosynthetic reaction that converts atmospheric carbon dioxide into glucose for plant growth, and oxygen.
Plants are the foundation of our planets food chain.
Human life on earth depends on our one star, the sun. Our sun is intrinsically variable with an energy output cycle of eleven years. Increased stellar output periods are associated with more sunspots, auroral activity, and damage to our cities power grids and orbiting satellites, and the increased risk of skin cancer from UV radiation. The variation is small enough to allow life on our planet. Some stars vary tremendously which theoretically would prevent stable life from evolving.