Meaning: This sentence is describing the trees moving or swinging back and forth and making a harsh, squeaking sound during the storm.
Choice of Words: The word "swayed" means to move or swing back and forth. "Creaked" means to make a harsh, squeaking sound. "In the storm" means during the storm. When you put them together, "The trees swayed and creaked in the storm" means that the trees moved or swung back and forth and made a harsh, squeaking sound during the storm.