Thinking out of the Box?!

I hear and say that expression a lot, yet I was wondering what is that box that we encourage thingking out of it. At first glance it came to me that may be it's reality that you need to think outside its bounds in order to be able to ocme up with creative ideas? Yet I think again and find that any idea or solution will have to be carried out in the reality we all live in. May be it's just the constraints that we should avoid thinking of in the early stages? You just let your mind wander, no constraints.. no limits.. no boundaries.. no borders should ever exist in 'ideas land'! The filteration to see the more suitable ideas should come at a much later stage. They shouldn't come early or else they will kill the idea when it's still a newly born, too weak and fragile to stand up for judgement and criticism. Another thought that came to my mind is that may be that box is traditions, ad that thinking inside that box would mean you are entrapped in traditional thinking. Those packages of canned ideas they impose on us and throw in our heads since our childhood, powerfully limiting our imagination and creativity and limiting our capabilities of analysis and coming up with our own conclusions and resolutions. They are too scared of the last part specifically. We are supposed to adopt the exact same ideas, the very same pattern of thinking as they are considered tried and true. They are considered the safest way to go, yet it results in the sedentary life that's freezing the minds of all of us, not giving us room for experience and self-development.