Q: “What Are The Differences In The Various Types Of Magnets Uses In Guitar Pickups?”
A: All guitar pickups have the same basic structure: a magnet (or two) surrounded by a coil. The two common types of magnets used in pickups today are Alnico (Alnico II or Alnico V) and Ceramic. Though your perception and your ears may vary, Alnico II is generally thought to provide a warm tone with slight emphasis on midrange frequencies. The output level of Alnico II is lower than Alnico V. Alnico V is usually perceived as a brighter (more high-frequency response), glassier tone, with higher output levels. Ceramic magnets are even brighter still, with faster attack transient response and a higher output.
If you feel your guitar is too bright sounding, you could try replacing your pickup(s) with Alnico II models to darken it a bit. Conversely, to make your guitar stand out for solos or to cut through a dense band mix, an Alnico V or Ceramic pickup could brighten your tone.