Hi Mary. I found several articles on this. You can just google it if you want to. But synthetic potassium is potassium this is "created" to simulate real potassium. Sort of like beauty products that have synthetic Vitamin E in them. They can mimic the real thing, but they don't work as well and are not good for you. The potassium in bananas and things such as coconut water are naturally found in those foods and they are in their pure form. Your body really can't assimulate synthetic foods. But the body can absorb and utilize foods that are natural. Gatorade is full of synthetic stuff and sweetners.
Mmmm...that doesn't really agree with the science I know. Potassium is an element; in its atomic form, all potassium is identical (and, while there are industrial processes to isolate potassium, they do so from "natural sources", i.e., potash). Googling "potassium natural artificial" produced nothing to support the idea that the potassium found in, say, a banana is different than the potassium found in a sports drink or a supplement.
There is a good reason to seek out micronutrients in food sources, however, and that is to keep the diet focused on nutrient-rich food. Getting potassium from sources such as bananas or cherries, which contain other useful nutrition, is preferable to supplementing an empty-calorie diet (which is more likely to be a diet high in refined and processed foods) with potassium supplements or sugary sports drinks.
(Edit: I would also say that potassium from a sports drink is vastly preferable to heatstroke)