There are four main ways of grinding coffee beans, pounding, rolling, chopping and burr grinding.

Pounding is used for Turkish coffee where the grounds need to be very fine, almost powdery as the coffee is put in a pot without a filter.
This is usually done with a pestle and mortar though a mill is starting to be come the norm these days.

Rolling coffee beans is done by grinding the coffee beans through 2 corrugated rollers.
This method produces a even, consistent grind and there is little heat to damage the coffee.
Due to the size of the machinery and the costs included, this method is used exclusively by commercial coffee roasters and retailers.

Chopping is done by fast moving blades in a enclosed container. These are usually specifically designed for the task but this can be done in a standard blender.
Chopping gives varied results, often ending with a mix of coarsely and finely ground coffee which in not desired for good coffee extraction.
Coffee choppers are cheaper to produce and as such are usually only produced for the domestic market where the cost of a burr grinder can be prohibitive.

Domestic coffee chopper and top view of the blades

Burr grinders use disks or conical grinding elements which the coffee beans are ground between.
This constant distance, similar to rollers, allows for an even, more consistent grind.
A consistent grind produces a better cup of coffee when filtered or used in an espresso machine.
Burr grinders also produce very little heat so don’t effect the taste of the coffee.
They are the standard for commercial coffee grinders and used in the majority of coffee shops and quality coffee retailers.
Burrs are also used on high end domestic coffee grinders, though these tend to be the slightly cheaper disk types.

Commercial coffee grinder with hopper

Commercial coffee grinders usually have a hopper on the front allowing coffee to be ground in batches then quickly dispensed when needed.
This is very useful for very busy coffee shops as it saves on time, however when the ground coffee is left it quickly goes off, with a noticeable difference with in 20 minutes.

Becoming more popular are on demand grinders, as the name suggests these allow the coffee beans to be ground on demand, ie when the coffee is needed.
On demand coffee grinders are suitable to all but the very busiest coffee shops as the grinding only takes 5-10 seconds but makes sure the ground coffee is fresh every time.

Commercial on demand coffee grinder