If you're trying to broaden your understanding about dimensions, one of the first little roadblocks to be aware of is semantics regarding the 4th dimension. The first three dimensions roughly translate into width, height, and depth (both in physics and math). The fourth dimension in physics is time, referred to in theories regarding the spacetime continuum (for example, Einstein's theories). From what I can tell, in physics, some don't even call it the 4th dimension because it is not considered to be a spatial dimension. So in physics, there are the three spatial dimensions and the time dimension.

There is mathematical evidence of a 4th spatial, or Euclidian, dimension (and more).(Models of tesseracts and hyperspheres are attempts to illustrate the 4th spatial dimension in ways we can grasp from our 3-D perspective.) Additional dimensions are also hypothesized in physics theories such as string theory (10 dimensions) and M-theory (11 dimensions).

So the term 4th dimension can refer either to time, or a 4th spatial dimension, and it's important to know which is being discussed.