A jigger is a small tool that bartenders use to ensure that they are pouring the perfect amount of liquor into each drink. This is important because it helps to maintain the correct ratio of ingredients, which is essential for creating a balanced cocktail.
A jigger typically has two parts of different sizes, so that you can use it to measure both small and large quantities. Jiggers are usually made of metal or plastic, and they often have a graduated scale printed on the side to help you get the measurement just right (e.g. 1 ounce, 2 ounces, etc.).
When using a jigger, it is important to hold it level so that you get an accurate measurement. This is especially important when making cocktails that require precise amounts of ingredients.