The word 饼干 (bǐnggān) is a relatively modern term in the Chinese lexicon, reflecting the introduction of Western foods into China. While China has a rich history of its own pastries and snacks, collectively known as 点心 (diǎnxin), these are typically distinct from Western-style baked goods. The key cultural and linguistic takeaway is the categorization. An English speaker meticulously differentiates between a sweet, chewy chocolate chip cookie, a savory, salty cracker, and a buttery shortbread biscuit. In Chinese, these all fall comfortably under the 饼干 umbrella. This isn't a lack of nuance, but rather a different system of classification. The primary classification is based on form and texture: small, flat, and dry. The flavor (sweet vs. savory) is a secondary detail specified with an adjective. For example, Oreos (奥利奥 - Àolì'ào) and Saltines are both considered types of 饼干. This broadness makes it a very efficient and high-frequency word for learners to master.
饼干 is a common, everyday word used by people of all ages. You will encounter it constantly in supermarkets, convenience stores, and casual conversations about food.