Most people want to gain muscle and lose fat. This is one aspect "toning". Muscles can only get bigger or smaller, and become more or less visible due to body-fat variations. After six months of training, you can't gain muscle and lose fat both at the same time; this is due to the fact that gaining muscle requires an energy surplus and losing fat requires an energy deficit.
However a muscle can remain slightly contracted at rest which gives it a harder look. In addition it will be burning calories in this "toned" state so it is a double win situation.
But remember to get the muscle to become visible you have to lose fat first!