通俗 (tōng sú) describes language or culture that is easy for ordinary people to understand — it's the opposite of 'highbrow' or 'academic'. Unlike 普通 (pǔ tōng 'ordinary, average'), which describes something unremarkable, 通俗 has a positive sense of being approachable and popular. It is also distinct from 俗 (sú) and 庸俗 (yōng sú), which often carry a negative connotation of being vulgar or tacky.