并肩 literally means 'together shoulder' — combining 并 (bìng), meaning 'together, side by side', and 肩 (jiān), meaning 'shoulder'. It evokes the physical image of two people standing or walking with shoulders aligned, symbolizing close cooperation, equality, or shared purpose. Though it originates from a literal spatial arrangement, it’s used more often figuratively to describe partnership, solidarity, or parallel progress — especially in contexts like teamwork, friendship, or social movements.

The phrase functions primarily as an adverb ('side by side') or verb ('to stand/walk shoulder to shoulder'). It carries a positive, warm, and somewhat literary tone — common in speeches, essays, and descriptive writing, but less frequent in casual daily speech. You’ll often see it paired with verbs like 走 (walk), 站 (stand), 奋斗 (struggle), or 工作 (work) to emphasize unity and mutual support.