Fourier Analysis is the study of how complex mathematical formulas or trigonometric functions may be broken down into simpler components. This process is analogous to how cells in our visual cortex to enable us to see images. Basically, this means that when looking at an image, our brain converts the picture into its simplest units, composed of a series of light and dark bars.
Some mechanisms are responsible for coarse variations in light and dark, enabling us to detect silhouettes or the overall shape of an object. Other mechanisms are responsible for fine variations, which enable us to see the fine details of an image.
For example, when looking at a picture of a zebra, certain filters in our brain allow us to detect the overall horse-like silhouette, but we are able to distinguish the animal as a zebra because of other filters that detect the black and white stripes that our brain interprets as a zebra.