In addition to "direct" wh-questions that begin with a wh-word or wh-phrase, there are other wh-structures that can be embedded inside English sentences. The highlighted structures in the following sentences are "indirect" or embedded wh-questions:
Tell us who manages your company’s payroll system.
The supervisor doesn’t know what the accountant said.
The bookkeeper was curious about which marketing plan you were talking about.
The investors weren’t sure when your business begins its fiscal year.
The manager explained why the accountant debited that customer’s account.
These embedded questions differ from direct wh-questions in that the entire clause occupies an argument position. In the above sentences, the embedded questions occupy various object positions.
Embedded wh-questions also differ from direct wh-questions in word order. Although an embedded question begins with a wh-word or phrase, there is no helping verb between the wh-word or phrase and the subject of the embedded question. Compare the presence of does in the direct question,
When does your business begin its fiscal year?
with the following embedded question, which contains no helping verb before the subject your business:
Tell me when your business begins its fiscal year.
Wh-words and phrases can also introduce "relative clauses." In the following sentences, the highlighted relative clauses describe or limit the meanings of the noun phrases that they follow:
The bookkeeper was curious about the marketing plan which you were talking about.
The owner hired an accountant who will manage the company’s payroll system.