Rotation diets shift around the types of food you eat day to day so that your body cannot adapt to your diet as easily. Some of these diets will shift the number of carbs you eat day to day, while others will shift the content of meals day to day (for example you might have a high-carb, low-fat breakfast for two days, then the next day it would be low-carb and moderate fat.)
The point of these is to prevent your body from adapting to your diet plan. Plateaus and “sticking points” where you stop losing weight are common problems in many weight loss programs that often require some kind of change-up to work through them, but Rotation diets have a change mechanism built in. Often even before you reach a “sticking point”, your body will start to burn fat less and less quickly as it adapts to what you eating, and rotation diets can prevent this slowdown as well. The constant change-up will make it harder for your body to realize that it is losing fat, and it will be less likely to respond by doing such things as slowing down your metabolism. Especially if your body thinks it is starving, it will do what it can to slow things down.
Rotation is a good weight loss principle no matter what diet you are on, and several diets make it the cornerstone of their program. The problem is that you still need to make sure that the rest of the diet plan is sound and will work well in conjunction with rotation. The advantage to specific Rotation diet plans is that that they will have a plan to follow if you are not good at figuring out how to do the rotation yourself.