Meaning: This sentence describes a sunny day with birds singing happily.
Choice of Words: "Sun" is the star at the center of our solar system, and "shines" means to emit light and heat. "Birds" are warm-blooded vertebrates with feathers, and "tweet" is the sound they make. "Happily" means feeling or showing pleasure or contentment. Together, it creates a cheerful image of a sunny day with birds singing.