Coffee Grinder - Blade and Burr Grinders

Blade Grinder

A blade grinder chops the beans with a spinning blade attached to a motor. The blade is similar to that of a propeller. The fineness of the grind is determined by how long you let the grinder operate. The longer it grinds the finer the coffee becomes.
Blade grinders are usually less expensive
The blade grinder will create a range of particle sizes, from large to small.

Burr mill grinder crushes the beans with a grinding wheel. It produces a more consistent grind and will not burn the beans. To make a finer grind, you make an adjustment that moves the two plates closer together.
Burr grinders are usually more expensive than blade grinders.
In general the burr grinder makes a more uniform particle size.