The format of the file will depend on the output device it's going to run on. Clients who know what they want don't ask for file formats arbitrarily. Images that are going to be viewed directly on a device have different resolution and color space requirements than -editing software also includes settings for specific printing methods in the industry. For example your image look is going to change if it prints on uncoated versus coated paper stock and there are software settings to deal with that. The best way to handle what a client is asking for when you don't understand it is to get their output vendor's contact information so you can confer directly with them. Good print vendors will have documentation on the specific settings they require in your software program as well as templates for standard items they manufacture which can help you lay out your file properly.