This.
People need to forget about terms like "toning", "shaping", "sculpting", etc. A muscle can really only do two things: it can grow larger or it can shrink. The shape of your muscles is determined by genetics and cannot be changed. When your muscles grow they may appear to change shape, but ultimately the shape of your muscles is determined by genetics.
To make a muscle appear more defined, lose bodyfat.
Diet is also very important. Eating more calories than you burn is necessary for muscle growth. Eating fewer calories than you burn is necessary for fat loss. I'm sure sooner or later someone will quote me saying you can do both at the same time, but unless you are a total beginner with a decent amount of fat to lose and/or have elite genetics, it really doesn't work very well.