Meaning: The star in the middle of our solar system gave off a lot of light on that particular day.
Choice of Words: Sun is the star at the center of our solar system. It provides light and heat to the Earth. Brightly means with a lot of light.
Alternative Expressions
The sun was shining brightly that day.
Meaning: This means the same thing as the first sentence, but it uses the verb "was shining" instead of "shone".
Choice of Words:The sun is the big, bright star in the sky that gives us light and heat. Was shining means that the sun was giving off light. Brightly means with a lot of light. That day means on a particular day in the past.
It was a bright, sunny day.
Meaning: This means that the day was full of sunlight and that there was a lot of light.
Choice of Words:It refers to the day. Was is a verb that means to exist or to be. A is an indefinite article that means one. Bright means full of light. Sunny means full of sunlight. Day means a period of time from sunrise to sunset.