Body confusion keeps your body guessing about what's coming next. If you eat low fat. low cal, or whatever way you eat and all of a sudden you aren't losing, eating a day of higher fat, cal, etc. can jump start you into losing again
I eat lower carb so just by doing 1 day a week of eating higher carbs (reload) my body is like "Oh look body! We don't have to start storing the extra carbs we were craving as body fat since just got more carbs then we thought we were getting, come on muscles, it's feast time for your glycogen stores!"
Everyone is different but I use carbs for muscle growth. Any extra just makes me sluggish and tired and will be stored as fat so once I knew the amount I needed I cut out all the excess with the exception of my reload day.
I hope I didn't confuse you, maybe someone else can explain it better.