What is the primary purpose of a beer's head when poured?

The primary purpose of a beer's head when poured is to provide aromas. When beer is poured, the foam created—commonly referred to as the head—traps volatile aromatic compounds released during the pour. This foam enhances the sensory experience by retaining these aromas and allowing them to be released as you drink.

The head can also influence other aspects of the drinking experience, such as the perception of carbonation and mouthfeel. However, the most distinct and significant role of the head is its ability to concentrate and enhance the beer's aroma, making it a crucial aspect of enjoying the full character of the beer. This aromatic component is essential for evaluating the beer's style, ingredients, and overall quality.