Pied-piping
Many instances of wh-fronting involve pied-piping. Pied-piping occurs when a fronted wh-word (or otherwise focused word) pulls an entire encompassing phrase to the front of the clause with it, i.e. it "pied-pipes" the other words of the phrase with it to the front of the clause (see the the Pied Piper of Hamelin). The following two subsections consider both obligatory and optional pied-piping.
Read more about this topic: Wh-movement