At a high level, an object is a collection of behaviors and data. At the edges, some objects are strictly behavior, while others are little more than data. Some objects mimic things we know from the real world, while other objects capture abstract notions that have no direct counterpart in the physical realm. Some objects are abstract templates intended for refinement by "concrete" subclasses.

CGI::Application is an interesting case. It is sort of a template function that encapsulates a switch on data provided from URI arguments. Is it a shining examplare of object modeling? Debatable. Should you be "allowed" to use it. Sure.

If you really want to understand objects at a deep level, I recommend that you spend some time playing with Smalltalk. In Smalltalk, everything is an object, including some abstract things like Classes and Processes. Squeak Smalltalk is freely downloadable.