It all depends on the product you choose. If you use a Chemex or a hand filter, for example, you'll be preparing your filter coffee using the pour-over method. This means you place a suitable filter into your maker and fill it with coffee grounds. Then, you pour hot water over the filter, and the coffee begins to drip into your collecting container, such as a cup or coffee pot.
However, if you use a French press, better known as a coffee press, you don't need coffee filters. With this brewing method, you pour the ground coffee beans directly into the pot and pour over hot water. After a short rest, place the plunger on the pot and slowly press down to force the ground coffee toward the bottom. Therefore, you should grind your coffee medium to coarse with this brewing method.
The AeroPress, on the other hand, works similarly to a French Press, but requires a paper coffee filter. This filter is used to filter the coffee-water mixture at the end of the brewing process. This gives you complete control during preparation!