A Marker of Regional Identity: Erhua is the quintessential sonic signature of Northern China, with Beijing as its epicenter. The standard for Mandarin pronunciation (普通话 - pǔtōnghuà) is based on the Beijing dialect, which is why erhua is taught in textbooks, even though it's used much less frequently in Southern China, Taiwan, and Singapore. For many Chinese people, a heavy use of erhua immediately signals that the speaker is likely from Beijing or the surrounding Northeast regions.
Formality and Perception: Erhua lives firmly in the world of spoken, informal language (`口语 - kǒuyǔ`). You'll hear it constantly on the streets of Beijing, in casual chats with friends, and in folk songs. You will almost never hear it in a formal speech, a university lecture, or a national news broadcast, except for a few standardized words like `这儿 (zhèr)` or `那儿 (nàr)`. To a Southerner, excessive erhua might sound a bit folksy or even “like a country bumpkin” (土), while to a Northerner, its absence can make speech sound stiff and overly formal.
Comparison to Western Concepts: The function of erhua can be compared to diminutive suffixes in English like “-y” (doggy), “-ie” (birdie), or “-let” (piglet). These suffixes make the noun seem smaller, cuter, or more affectionate. Erhua does this with sound (`花儿 huār` - a little flower). However, erhua is more versatile. It's not just a suffix; it's a phonological change that also functions to add a casual, conversational flavor, much like using contractions (“gonna” instead of “going to”) or colloquialisms in English to signal informality.