A Product Configurator is a set of 'rules' that describe a product family. The rules can include questions that are asked to get options and specification elements. The answers to the questions are used to construct product structures that are appropriate to the answers. For example, if a question asks 'What colour?' then the product structure could be constructed to call up the appropriate colour paint.

Product Configurators are just a short-cut to creating product structures. The end result is the same as if you did it by hand.