We are used do the idea of 2D and 3D, but how many dimensions are there? Dimensions are considered as degrees of freedom, and our nervous systems have evolved in a way which allows us to percive some of them. A single eye can collect data from two dimensions, and two eyes can collect data from three. It is possible that these dimensions we can observe are not as they seem. String theorists say that there are 13 dimesions to the universe, but other theorys state that there could be zero, or an infinite number of dimensions, and what we see is just an illusion of perception. When we look at something, parts of our brain use the data from the eyes to create a spatial image in the visual cortex, and this is what we 'see'. This process allows us to percieve objects and relative distances in 3D, but we never see a whole object at once, and therfore are not seeing the full three dimensions. Higher, or multiple dimensions can be difficult to visualize. The following article by Blaze Labs, and this article from the 1940 Journal of Educational Psychology (found here) should help you gain a clear understanding of N-Dimensions.

Existence of Higher dimensional space & Perception of time
Understanding 1 dimensional space
Understanding 2 dimensional space
Understanding 4 dimensional space
What's the evidence for the existence of higher dimensions?
Can dimensions be limited, or is the universe really infinite?

Next Page: Existence of Higher dimensional space & Perception of time
Previous Page: Electromagnetism - Coils