Learn Spanish (Latin America): ¿Qué es esa cosa?

When you are asking to identify an object or asking for a definition (like "What is that thing?"), you always use qué + es. You would use cuál when asking someone to choose from a group, like "Which one?"

Why does Qué have an accent mark?

In Spanish, all question words (like qué, quién, and dónde) get an accent mark. This helps tell them apart from the exact same words when they are used in regular statements (like que, which usually means "that").

Could I just say ¿Qué es eso? to mean "What is that?"

Yes! If you point at an unknown object without using the specific word cosa (thing), you use the gender-neutral eso: ¿Qué es eso? But because this sentence includes the feminine noun cosa, we have to use the matching feminine word for "that", which is esa.

Why do we use es instead of está?

We use the verb ser (here as es) to identify what an object is. Since you are asking for the basic identity of the thing, es is correct. The other "to be" verb, estar, is used for locations or temporary states, not for identifying what something actually is.