The world around us is three-dimensional. What does that exactly mean? Roughly speaking, we are able to move in three different directions (from left to right, from front to back and from top to bottom) in order to move from an arbitrary point A to a point B. Slightly differently: we have three different coordinates needed to describe every point in our space.
Flatland: A Romance of Many Dimensions is written by the English schoolmaster Edwin A. Abbott, first published in 1884, describing two-dimensional beings that interact with each other. In the same way that he describes you can understand the three-dimensional world and it’s beyond dimensions using the same analogy.