The Five Kingdoms is the name given to the last political entity which existed in the Southern Kingdoms. They were a cooperative effort between five different kingdoms, each ruled and mostly occupied by a different race: human, elf, dwarf, gnome, and halfling. It is considered a time of almost utopian cooperation between the races.
Given the chaos towards the end of its existence, and the closing off of the whole Southern Kingdoms, much knowledge about the Five Kingdoms has been lost.
Selinar was the name of the Artificer for the Elven Kingdom.