Dip-dye basically means to dye parts of your hair another color. Bright hues, pastels and the popular "ombré" gradient shading are all popular hair colors. I particularly love it when a brunette lightens the ends just a bit in an ombré effect that's super popular right now (see my photo gallery of ombré hairstyles).
You can get this look in a variety of ways. You can do it yourself, have a pro do it or use a less permanent solution via clip-in extensions, Kool-Aid mixes (yes, you read that correctly) or spray color.
If you do decide to go the more permanent dip-dye route, consider that if you have dyed hair or dark hair, you will likely have to bleach the hair that will be colored first. This can be harsh on your hair. If you are naturally blonde, you may be able to dye without bleaching.
More on hair color: