I'm dieting on a daily basis, but I'm not working out. Will I be able to lose weight just by diet or do I have to workout and exercise? I just can't understand.
You lose weight when you consume less calories than you burn. You burn calories even when you do not exercise, because your body needs calories to maintain vital functions of the heart, kidneys, brain, to digest food, produce heat, etc.
So, even if you lie in bed all day and consume less calories than you burn, you will lose weight.
If you, as a sedentary adult, burn, for example, about 2,000 Calories per day, you need to consume less than this, let's say 1,500 Cal per day and you will lose weight, exercising or not.
How do you know how many calories do you burn? If you consume a certain amount of calories and your body weight remains stable for several weeks, you know that you consume about as much calories as you burn. So, you can count how many you consume and you will know.
To lose weight, it seems reasonable to consume about 500 Calories less per day than you consume. This is a deficit of 3,500 Calories per week, which equals about 1 pound of body fat.
Exercise is associated with several health benefits (systematic review, PubMed Central). You do not need to "work out" to call it exercise. Even walking is exercise.