Meaning: This sentence tells us what the rain is doing in the sky. It's like saying,
Choice of Words: The word "rain" is water that falls from the sky in drops, "falls" means to move downwards, "from" means starting at a particular place or time, and "sky" is the area above the earth where you see clouds, the sun, and the moon. When you put them together, it means that the water that falls from the sky in drops is moving downwards starting at a particular place or time in the area above the earth.