Indirect questions - also called interrogative content clauses - are subordinate clauses that serve as the object in a main clause. Usually they are the object of a verb of telling, knowing or questioning. As a form of "W" questions, they begin with a question word.

Indirect questions can be turned into direct questions that also contain a question word. An indirect question using the subjunctive II construction sounds more polite than a direct question.

Examples:
Indirect question: Könnten Sie mir sagen, wo Ostrowski arbeitet? (Könnten Sie es mir sagen.)
Direct question: Sagen Sie mir bitte: "Wo arbeitet Ostrowski?"

Indirect question: Ich möchte nur wissen, wo Ostrowski arbeitet. (Ich möchte es nur wissen.)
Direct question: Ich möchte wissen: "Wo arbeitet Ostrowski?"