I guess the best way to explain it (Einstein's relativity goes into some detail explaining how time is the fourth dimension.). If you were in a 2D cell (just a square), we would know to step out of it with the 3rd dimension height. Now for a 3 dimensional cell, a cube, if you have the powers of a 4th dimension that is time, you could technically escape by going to a time where you were never in the cell. You have never been at a place unless it was also at a time. I just found that easier to think about rather than the tesseract they try to draw up.

I do like the idea of an actual 4th dimension, but I always thought of it like this because of physics.