A 4-dimensional object is an object entirely made up out of 3-dimensional objects. We cannot fully grasp or even try to understand this concept with our minds because there is nothing like this in our world. Instead, we have to use animations to even slightly try to understand what these odd shapes are.
More info:
http://im-possible.info/english/articles/hypercube/index.html
![Image result for hypercube](https://www.mathcurve.com/polyedres/hypercube/anaglyphe_hypercube_cabri.gif)
Source: https://www.mathcurve.com/polyedres/hypercube/4-hypercube.shtml