A sweatshop is a factory or small workshop where people work very long hours for very little money, in conditions that are hot, crowded, dirty, or dangerous — and the word always says the speaker thinks this is wrong. You cannot use it neutrally; calling a place a sweatshop is an accusation. It is most often used about clothing, shoe, and toy factories that make goods cheaply for rich countries, which is why you meet it beside words like 'sweatshop labour', 'sweatshop conditions', and 'made in a sweatshop'. The word is old — it comes from the 1800s, when a middleman called a 'sweater' would squeeze work out of poor people at home or in tiny rooms — so the 'sweat' here is not really about heat; it is about the money and effort being squeezed out of the worker. People also stretch it in a joking, exaggerated way about an ordinary hard job: 'This office is a sweatshop' just means the boss asks too much. Everyone hearing that knows it is not literally true.