Different types of coffees require different type of grinds. For instance, a fast brewing method like the espresso requires a finer ground where as for a slow brewing method like the french press, the coffee grind needs to be coarse. when the grind is fine, more area of the beans is exposed to water which results in a strong brew, whereas when less area is exposed as in case of a large grind size, less hot water can get in conact with the beans.
Coarse grind is usually used for making coffee in a percolator, a vacuum coffee maker or a french press as their filters are iopen pore, being coarse grind, the beans cannot escpae through the filter and into the coffee.
This type of grind is ideal for drip
coffee makers, both the manual and automatic variety. A gold filter can be very useful in this case as it wont let any coffee sediments into your cup.
Espresso is what needs this type of a grind. The grind is as fine as confectioner's sugar and the resulting drink with this type of grind is rich in taste.
Very fine grind
This type of grind feels almost as fine as flour. Turkish coffee gets its heavy and rich taste by using this type of a grind.