Hi, I am not really on IF but I see no one has responded to you so I will try to explain.
IF stands for intermittent fasting and this simply means that you follow your own fasting pattern.
You will have a window period for eating and a period in which you can’t eat anything at all.
For example, if you are doing a 6:18 IF it means you will have a 6 hours window period of eating and an 18 hour period of no eating. The eating period can start at any time, you could say your 6 hour ration period is from 12 midday until 6 pm, there after you don’t eat until 13 midday the next day.
Hope it makes sense