啥子 is a dialectal pronoun meaning 'what' or 'which thing', most commonly used in Southwestern Mandarin (especially Sichuan and Chongqing). It is the colloquial equivalent of standard Mandarin 什么. Learners should be aware that 啥子 is informal and regionally marked — using it outside of those dialects may sound out of place. The word can appear in questions and exclamations just like 什么.