It is a common question used to ask about something that is unknown or unclear.
Here are some examples of how it can be used:
* "Que es eso?" (What is that?) *You point to something you don't recognize.*
* "¿Que es eso que está en la mesa?" (What is that on the table?)
* "¿Que es eso que estás escuchando?" (What is that you are listening to?)
Let me know if you have any other Spanish questions!