There are two primary methods a modern cartridge uses to generate current. These are moving magnet (MM) and moving coil (MC) configurations. Many moving coil cartridges come in high and low output versions. In order to better understand the differences between the two it is necessary to briefly discuss methods of generating electricity, as well as provide you, the reader, an amusing anecdote about my youth.
Let's travel back in time together to science class. My 8th grade science teacher delighted in demonstrating to us a small hand cranked generator. In hindsight his methods were quite masochistic. He would line us up and eloquently explain the wonders of electricity by giving each of us a mild shock. After all of our fingers were zapped, and he had briefly made each of us accountable for being disinterested in science class, our status quo arrangement of politely ignoring one another resumed. I did however develop a rudimentary knowledge of electricity, as well as a distrust of science teachers, that I retain to this day.
Basically moving magnet cartridges works in the same way as that, or any other generator. By moving a magnet within copper coils a small voltage is created. It breaks down like this:
Moving magnet cartridges tend to produce lush, mellow sound. They are available in a variety of shapes, sizes and levels of quality. Most MM cartridges have replaceable styli. Their high voltage output, variety, and the availability of stylus replacement make Moving Magnet cartridges a great choice for the beginner and audiophile alike.
Right about now your probably asking, "Brian, if moving magnet cartridges are so great then why do they make Moving Coil Cartridges too?"
For you, gentle reader, I will attempt to explain:
Moving Coil (MC) cartridges work in a similar way to MM cartridges. The primary difference being, as your stylus tracks it vibrates tiny wire coils around a magnet. Many audiophiles prefer moving coil setups. MC cartridges tend to display better tonality, transparency, imaging, and also tend to create less distortion than their MM counterparts.
A moving coil setup requires much more consideration for you system, as well as a familiarity with audio component setup. Moving coil cartridges are not always the best idea for a beginner. Many MC cartridges will not work in pre-amps designed for MM cartridges. Modern receivers often do not have an input for turntables (this section is usually labeled "Phono"), if your receiver does not have this feature you will need a separate pre-amp to drive your turntable, and an open auxilary plug-in. If your modern, or vintage receiver does have this section you will need to know if it is configured for MM or MC. If the unit is not clearly labeled your manual will provide you with specifications. Some receivers have a switch built in (usually near the RCA plug-in for your table) that can dive either MM or MC, this is rare but not unheard of, especially in high-end audio components.
Many manufactures produce high and low output versions of the same cartridge. Benz Micro for example produces the Benz Gold (0.4 millivolts) and Benz Silver (2.0millivolts) thought they have different names and are different colors they are, save the output voltage, the same cartridge. Other manufactures produce both high and low output cartridges that are dramatically different from one another. High output MC cartridges can usually be used with pre-amps configured for MM setups.