The Sun is the ultimate source of energy in our solar system and for the planet Earth. The light from the Sun makes the surface of the planet the correct temperature for liquid water to exist and by extension for organic life as we know it to exist. The energy from sunlight is harnessed by plants via the process of photosynthesis to make food. This food is the start of the food chain for all organisms on the planet. The warmth of the Sun also powers the climate and weather patterns for the entire planet. So as you can see, the Sun makes everything you see possible on Earth.
The sun provides light which is necessary for photosynthesis. As a result, glucose and oxygen is released which is necessary for cellular respiration which is necessary for humans to survive.