As gardeners, it's important to understand basic principles of plant life. And more critical than everything else is the fact that plants need light. It doesn't take many years of trial and error in the garden to learn that you must learn the light preferences of each plant and provide the right amount of light to that plant as closely as possible. Certainly other factors like soil, drainage, and climate are important, but nothing else matters if you don't get the light correct.
We use some standard terms to describe light conditions, but it's possible gardeners don't all understand exactly what these terms mean. "Direct sun" means direct sun fron sun up to sun down. Then we have terms like "full sun," "part sun," "part shade," and "full shade." These decrement in roughly two-hour increments, starting with "full sun," meaning eight hours of sunlight per day. "Part sunlight" would be six to eight hours of sun per day, and so on.
The light preference of our garden plants are based on the natural habitat of their ancestors. Whether the ancestors grew in native sunny fields or if they grew on the forest floor, that affects what light the cultivated plant needs.