anthony81212 is closest. The small ice chips are created by fast, vigourous shaking. Yes, post shaking drops a few in as well but most were poured in with the rest of the drink. Yes they are delightful on the lips, but they are the sign of a watered down cocktail.
Unfortunately , too many bartenders don’t truly understand what exactly they are doing. They want to shake it hard and long to make it as cold as possible. They’re wrong. Shaking a cocktail mixes the ingredients. To chill a cocktail you stir. With shaking you are inevitably going to melt some of the ice (water down the cocktail) so you must work fast. The cocktail glass must be chilled in advance. Combine all the ingredients quickly in the shaker and give it 5 (only five!) quick, vigorous shakes over your shoulder. The cocktail should be strained out of the glass tumbler, not the silver shaker. You will recognize a “lesser” bartender immediately because they pour out of the silver shaker. This allows them to be less accurate with their freepouring and shows they don’t have the best grasp on the recipe. Also they’ve just spent 15 seconds shaking it. They don’t want you to see how little ice is left in the shaker.