One very common word in English is "what". It also has a simple translation in Mandarin.
什么 (Shénme) is the word for "what".
On it's own, you can use it in a sentence the same way we do in English.
什么? (Shénme?) is equivalent to "What?"
Some more examples are:
那是什么？ (Nà shì shénme?) is "What is that?" (Notice the order is different to English. Literally, it's "that is what?").
你叫什么名字？ (Nǐ jiào shénme míngzì?) is "What is your name?". (Again literally, it's "you call what name?".