Baking by weight is much more accurate than volume. When using US standard cups, ingredients like flour and sugar can easily be overpacked into the cup causing you to add too much of certain ingredients. Recipes with weight measurements are also easier to scale to smaller or bigger batches without dealing with weird fractions. To measure by weight, you simply need a kitchen scale which you can usually pick up for less than $20. Small measurements are given in tablespoons and teaspoons because most kitchen scales are not accurate under about 10g. Tiny amounts like a ¼ teaspoon may not register accurately unless you have a drug scale. Mixing these measurements is a common practice among other recipe sites and commercial kitchens.