It's often used in a more general sense than the English "language," referring to any spoken or written language.
Here are some examples:
* "El idioma español es muy bonito." (The Spanish language is very beautiful.)
* "Ella habla varios idiomas." (She speaks several languages.)
* "¿Cuál es tu idioma nativo?" (What is your native language?)
So, if someone asks you "What is the idioma?" they are asking you what language you are speaking or referring to.