Yup, it's just plain ol' fasting... done intermittently. Well... sometimes? A lot of people do scheduled or daily fasts, so there's no "intermittent."
You can do it a number of ways: let it happen naturally, choose a fasting window, don't eat in the mornings, etc. It's something most people experiment a bit with. Start slow and see how you feel when you do it, then think about whether you want to make it a regular part of your lifestyle.