Tone versus definition
Commonly misunderstood. Muscle tone refers to "tonus". This is nothing more than muscle tightness. Tone has nothing to do with seeing the striations and detail in the muscle, though. That's definition.
So, tone is only accomplished through exercise. There are many different techniques used to improve muscle tone... and no, high reps is another common misconception. Doing endless repetitions of an exercise is not the best way to improve muscle tone. An exercise regimen that starts with full range movements to help build muscle, followed by shorter range or fully contracted movements is best. By "shorter range" I'm referring to movements that neither reach full flexion, nor full contraction. This is a great technique for building lactic acid in the muscles, as well as achieving the resulting pump.
From there, my favorite technique for building tone is to hold the full contraction for a three count. Don't count reps! Count only the contracted portion. Falling between the ten to twenty rep scheme seems to work best. If you have a workout partner, or can just grab someone at the gym, have them count for you. Don't have them count aloud! Another technique would be to use the rep number at the end of the three count ie: 1...2...1- 1...2...2- 1...2...3- 1...2...4, and so on.