If you are an overweight or obese adult, you probably eat too much i.e. more than you actually need. As a matter of fact, your body needs a certain amount of calories to keep itself functional and active, and if you eat or drink more than that, you will likely gain weight. Likewise, if you consume fewer calories than you expend, you will lose weight.
Is weight loss the same as weight control? When you are not in control of something, you find it difficult to maintain it where it is. When you are not in control of your weight, you tend to lose weight or gain weight. So when you are in control of your weight, you would be able to maintain your weight more or less steady or gain or lose it as you will.