Chakra

The chakra nature system is simple:
Fire is stronger then Wind
Wind is stronger then Lightning
Lightning is stronger then Earth
Earth is stronger then Water
Water is stronger then Fire

Chakra paper is used to determin what the person's infinity chakra is.
The Chakra Paper reactions are as follows:
Fire: the Paper will ignite and turn to ash.
Wind: the Paper will split in two.
Lightning: the Paper will wrinkle.
Earth: the Paper will turn to dirt and crumble away.
Water: the Paper will become wet/damp.

No human alive could obtain all 5 chakra natures.
Kakashi has 4/5 due to his sharingan copying jutsu.
Kakuzu has 5/5 due to his earth grudge fear ability. -note earth grude fear is hidden so no one can auto say they have it.-
Rinnegan users are the only normal group that have all the natures.

When a character starts they are given one chakra nature.
Once they have reached Jounin or ANBU -since some ANBU are Chunin level- they obtain a second element.

Advanced Chakra natures, or Kekkei Genkai.
Ice Release is a mixture of Water and Wind. Only the Yuki clan has access to this chakra nature.
Lava Release is a mixture of Fire and Lava. Only through a kekkei genkai that Mei Terumi and Kurotsuchi know, it is unknown what clan they are in.
Storm Release is a mixture of Water and Lightning. Only known user is Darui, a clan is unknown.
Boil Release is a mixture of Water and Fire. Only known user is Mei Terumi, a clan is unknown.