Questions can be asked directly or indirectly. In an indirect question, a subordinate clause is formed from a direct question:

Direct question: Wieso reden nicht alle gleich?

Indirect question: Eva möchte wissen, wieso nicht alle gleich reden.

The subordinate clause, which is introduced by an interrogative, is often the object of the main clause. The subordinate clause, in this case, is also known as the object clause. In sentences composed of a main clause and an object clause, the main clause cannot usually standalone:

Was möchte Eva wissen?

Sie möchte wissen, wieso nicht alle gleich reden.

As in other subordinate clauses, a comma separates the main clause from the subordinate clause. The conjugated verb is usually at the end of the sentence.

The main clause can be a declarative clause or an interrogative. Look at the examples. Note the punctuation at the end of the sentence: if the main clause is declarative, it has a full stop at the end. If it is an interrogative, there is a question mark at the end.

Declarative clause + indirect interrogative clause:
Bitte sag mir, wo eine gute Sprachschule ist.

Interrogative + indirect interrogative clause:
Weißt du, was dieses Wort bedeutet?

Indirect interrogative clauses are often used to ask questions in an especially polite manner:

Ich möchte gerne wissen, wie man das auf Deutsch sagt.
Können Sie mir sagen, wo es zum Bahnhof geht?