A raindrop is a drop of water falling from a cloud. A typical raindrop is around 1-2 millimeters in diameter and, depending on size and altitude, falls at a rate between 2 and 12 meters per second.
Raindrops are not actually shaped like the iconic teardrop image we all learned to draw as children. Smaller raindrops are fairly round. Larger ones are flattened at the bottom by air resistance. The largest raindrops are about 8 millimeters in diameter and are usually the result of a melted hailstone.
Droplets of water smaller than about a half millimeter in diameter fall extremely slowly and do not splash upon contact with a puddle. These droplets are called drizzle. Droplets of about a quarter of a millimeter mostly remain suspended in the air, and this is known as mist. Smaller than that, cloud droplets and liquid fog droplets are around 0.1-0.2 millimeters and are simply too small to fall.