Staging is when a cook or chef works briefly, for free, in another chef's kitchen to learn and be exposed to new techniques and cuisines. A stage normally is used to see how a new chef or cook can adapt to the current environment in the kitchen. When a future chef is seeking an internship, often the stage is the next step after the interview.
A server or waiter can also "stage" in a restaurant for much the same purpose. The word is French, so it is pronounced with a short a (ah) followed by zje -- stahzje, mono-syllabic.