What is a Neodymium Magnet ?

More correctly known as a Neodymium-Iron-Boron magnet, a Neodymium Supermagnet is basically a block of the element Iron. Over the past several hundred years, it had been learned that as Iron is made harder, it makes a better magnet.
The element Carbon was first used to harden Iron into steel that made good magnets.

In the 1930's alloys of the elements Aluminum, Nickel, and Cobalt were mixed with Iron to give magnets far stronger than those of Iron or steel.
These Aluminum-Nickle-Iron-Cobalt magnets were called "ALNICO" magnets.

The next important step was to substitute the element Samarium in the place of the Aluminum and Nickel, making the Samarium-Cobalt magnet. Since Samarium is found in the part of the Periodic Table of the Elements called the "Rare Earth" group, Samarium-Cobalt magnets were often called "rare earth magnets".
The Samarium Cobalt magnets could be made many times as powerful as the best ALNICO magnets.

Another metallic element in the same "rare earth" group is Neodymium. When Neodymium, and a very small amount of the element Boron, are added to Iron, this material can be twice as magnetically powerful as the Samarium Cobalt magnets.

These Neodymium-Iron-Boron magnets are the strongest permanent magnets known and deserve the name "Neodymium Supermagnet".
Since Neodymium magnets loose some of their strength when heated to the temperature of a hot cup of coffee, another metallic element, Dysprosium, can be added to retain their magnetic strength at higher temperatures.