What is the difference between cornflour and flour?

Because cornstarch is pure starch, it has twice the thickening power of flour, which is only part starch. Thus, twice as much flour is needed to achieve the same thickening as cornstarch. To thicken sauces, cornstarch is combined with cold water first, which is called a slurry

So just go ahead and put this in your own words, hope this helped :)

Explanation:

To thicken sauces, cornflour is combined with cold water first, which is called a slurry. Flour, on the other hand, is cooked with fat and made into a roux. If you use cornflour in your recipes and you try to swap with flour you will need more of it to get the same effect. In general, it's recommended that you use twice as much flour as cornflour for thickening purposes. So if you need 1 tablespoon of cornstarch, use 2 tablespoons of white flour.