宝贝 (bǎobèi) has two main uses: as a noun meaning 'treasure' (a cherished object), and as a term of endearment for a loved one ('darling, honey'). As a treasure, it is more personal and affectionate than 宝 (bǎo, 'treasure, gem'), which is more general. As a term of endearment, it is a noun you call someone, unlike 亲爱 (qīn'ài, 'dear') which is an adjective, and it is warmer than 婴儿 (yīng'ér, 'infant') or 娃娃 (wáwa, 'baby/doll').