The phrase means cook now, serve later.
The methods, though, are numerous and vary depending upon the product, the time and available equipment, etc.
For instance, to hold a lasagne for an hour, it can be as easy as keeping it in a warm oven. However, to hold broiled fish would be darned near impossible. To hold a hollandaise sauce, precise temperature control is crucial.
In short, there is no one stop answer to how (or whether) to hold products for later service.