How do artists use gradation in their work? what does adding value gradation do?

Gradation of color and value can also be useful when painting other subjects. In a still life, for example, you might use a gradation in the background from left to right and from top to bottom. Please give me the brailiest answer?

:) Hoped this helped <3

well seeing i am an artist and i actually did a self portrait; i will describe how i painted it.   i used acrylic on a stretch canvas about 4 feet wide by 6 feet tall. i painted myself smiling in a soft pink long dress, white tile floor sitting on a white couch with a table behind and a vase of gorgeous flowers.   i also had a round white hat with a soft pink ribbon through it laying on the floor and on the table behind me was a lit candle. i kept it simple but soft and romantic.