'stuff' is mainly used as an all purpose word to mean 'things' or 'things like that'. It can refer to anything - physical things such as food, clothes etc or more abstract things such as information, ideas and opinions. It's a very useful word which we use all the time, and it's more natural than 'etc' or 'and so on' (which native speakers don't use in speech). So you'd say. What kind of food do they sell in that place? Oh, fast food - burgers, fries, hotdogs.... you know, stuff like that. Two points to add about the word: Grammar - 'stuff' is always uncountable (stuff/some stuff/lots of stuff) . So it can never be used in the plural ('stuffs' is wrong) and never with an indefinite singular article ('a stuff') is wrong. Formality - 'stuff' is quite informal, and shows a slightly 'dismissive' attitude to the subject. For example, a proud cook or artist might be insulted if you refer to their work as 'stuff'. Otherwise - do use it. It's a very useful word, when used correctly.

what is this stuff? 这是什么东西 / 玩意儿

stuff = 东西 / 玩意儿