"Dieting" describes any process of tracking and restricting your diet. For instance, I have type 1 diabetes, so I'm on a diet worked out together with my clinical dietician, which is separate from any weight loss issues. Eating vegeterian, eating healthy, etc. are all diets.

Secondly, when dieting to lose weight, you normally eat as many calories as you need - not less. You'll lose weight as long as you stop eating more than you need to get to your target weight.

Once you are at target weight, generally the process you use to maintain target weight is also called "dieting." (Generally we hear of it as losing weight because most people are over their target weight, and require higher willpower expenditures when they are.)