Meaning: This sentence describes the movement of an apple from a high position on a tree to a lower position on the ground.
Choice of Words: The verb "fell" means to move from a higher position to a lower one. "Apple" is a kind of fruit. "Tall" means very high. "Tree" is a large plant with a trunk and branches. When you put them together, the sentence means that an apple moved from a high place on a tree to a lower place on the ground.