While 拦 (lán) is a straightforward action verb, its most common cultural application is one every visitor to China must learn: 拦车 (lán chē), hailing a vehicle. In the West, one might say “hail,” “flag down,” or “get” a taxi. In Chinese, the concept is to “block” or “intercept” the taxi's path with your hand signal. This is a perfect example of 拦's core meaning in a daily, culturally specific context. Socially, the act of 拦 can be interpreted differently than in the West. Physically blocking a friend who is about to storm out in anger (你别拦我! Nǐ bié lán wǒ! - “Don't stop me!”) is a common, dramatic scene in Chinese TV shows. It's a direct, physical intervention that shows deep concern. While it could be seen as overly dramatic or physically imposing in some Western contexts, in China it can be a legitimate way to show you care enough to physically prevent someone from making a rash decision.
The use of 拦 (lán) ranges from everyday convenience to more serious obstruction.