Contractions in French questions

[kratsg]

Example question:
Est-ce qu'ils mangent avec les filles ?
qu'ils seems to be contracted for qui ils which translates to.. "who they"? If so, why is it normal to ask questions in this way?

[soundray]

"Qu'ils" expands to "que ils". Word by word, the beginning of the question translates to "Is it that they eat...".

[jdc465]

Besides inversion, placing est'ce que in front is a very common way to ask a question.