羔羊 literally means 'lamb' (a young sheep), but is also used figuratively to refer to an innocent, helpless person who is unfairly blamed for others' mistakes — much like the English 'scapegoat'. In Chinese, the figurative sense appears in formal or literary writing and in the fixed phrase 替罪羔羊 ('scapegoat'). Use it when you want to emphasize someone's vulnerability or the injustice of blaming them.