In the 3rd dimension, we can only see a half of absolutely everything we look at. In the 4th dimension one can see the the whole object at once, see basically through it.

i am from the 4th dimension

rawr

Basic explanation:

According to Einstein's special relativity, as one moves through space, one changes the way one measures space and time.
So space and time are linked, as a result, we say that there are 3 dimensions of space, and the fourth dimension is time.

In arts, however, the fourth dimension is often referred to as depth (just a side note).