Yttrium is one of the four elements named after the town of Ytterby, Sweden.
Yttrium is used in high-temperature superconductors, and in YAG (Yttrium-Aluminum-Garnet) lasers.
It is not, strictly speaking, a member of the Rare Earth group (Lanthanides or Actinides). But since it is in Group 3, it along with Scandium are often called Rare Earths.