I like to refer to gingham as plaid's weird cousin because gingham is like a branch off of plaid, though not included in plaid's direct family. (I've thought about this too much)
Many people often wonder what the difference is (if there is a difference) between plaid and gingham. As a plaid lover, it drives me crazy when someone has a gingham shirt on and calls it plaid. To clear up any confusion, and to know how to identify each, here you go:GINGHAM- Gingham is two stripes (normally the same width), in two colors (usually the second color is just a lighter shade of the first color), horizontally and vertically crossed on a white background (the background can be other colors than white.) Reminds me of picnic blankets and graph paper.
PLAID- Plaid is two or more colored stripes (the colors aren't just different shades of the other stripes, like in gingham), crossed vertically and horizontally, normally different widths, on a solid background. The stripes overlap to create squares of different shades.
Gingham Photo Credit: http://simpledesktops.com/browse/desktops/2012/sep/28/gingham-red/