贝 is a bound form (not used alone) meaning 'shell' or 'shellfish.' In ancient China, cowrie shells (贝) served as currency, so this character appears as a semantic component in many characters related to money and value, such as 财 (wealth), 贵 (expensive), and 货 (goods). In modern Chinese you'll encounter it in compounds like 贝壳 (shell), 宝贝 (treasure), and as a surname (贝).