Thinking outside the box means that you cast off the atmosphere that envelops you, step out of the box, leave all your experiences, mindsets and attitudes behind and start to view things from a completely different perspective: outside of the box; unfiltered, unbiased, open to suggestions, willing to empathize with others opinions, but also ready to swim against the flood and to think what no one else has ever thought of. It also means that you leave everything behind you thought you would know, everything that was thought to you in school and start to approach specific situations and problems from a completely different point of view than you did before.
In a metaphorical sense the box is your habitual mind, or the world you create in your mind, which represents the conventional you. It is a world made up of your beliefs, assumptions, irrational thoughts, mental habits, perceptions, desires, expectations, emotions, attachments, and memories. It is the Meta Program (your personality) which guides your thinking and actions.
Thinking outside the box is also described more technically as paradigm shift or paradigm change. In psychology it is termed as creative illumination, and in spirituality as total freedom or liberation. Out of the box thinking unleashes your creative and innovative thinking and helps you to generate new ideas and thoughts, or see the world differently from different perspectives.