A steppe is a very large, very flat piece of land covered in grass, with almost no trees. It is dry — not a desert, because grass grows — but too dry for a forest. We use this word mostly for one part of the world: the long belt of grassland that runs from Ukraine and southern Russia, across Central Asia (Kazakhstan, Mongolia), and up to China. So it is half a geography word and half a place name. If you say 'the steppe', people think of that specific land, the way 'the Sahara' means one desert. If you say 'a steppe' or 'steppes', you are talking about that kind of land more generally, and geographers do use it for similar grassland elsewhere. You will meet this word most in history and geography: horses, herders, the Mongols, people moving with their animals. It sounds a bit bookish — nobody in daily conversation says 'I went for a walk on the steppe'. Note also that the same word is used as an adjective in front of animal and plant names: steppe eagle, steppe wolf. One more thing: teachers often line it up with prairie (North America), pampas (Argentina), savanna (Africa, with scattered trees). They are all wide grassland; the difference is which continent, and how hot and how dry.