Chakra Affinities
Chakra affinity is of course the element a person is most in tuned with and such the easiest element they can make and manipulate. There are seven chakra affinities: Wind, Water, Fire, Earth, Lightning, Light and Dark, though only the first five can be found in any nation, though with variable commonness based on region. Each nation has a most common and least common nature.
Overall most common elements.
Earth
Fire
Water
Wind
Lightning
How common an element is in an area depends a lot on neighboring countries as well as regional variation. The five main elemental nations most common affinity matches the nation’s affinity, while their rarest affinity is the natural weakness to that affinity mostly because of the dominant type being most common.
A shinobi’s elemental nature often can and does denote what type of jutsu and thus what fighting style suits them the best. This is not the rule of course, as any variation on certain jutsu and styles can be followed by any shinobi.
There are other variants and stereotypes based on affinities as well. It’s said earth users are hardier, more patient and more physically inclined, fire users are aggressive and have a hot temper, water users have better control making them suited to being healers as well as fluid flexible nature, wind users are naturally faster than most people and tend to crave freedom, while lightning users have increased reflexes as well as quick tongues. While there might be some merit to the physical effects, asking a shinobi their elemental affinity to determine their personality is much akin to asking their horoscope sign or their blood type. Basically bullshit as such things like that don’t really affect how a person would act in any given situation.
As far as the characters in story go, some of them follow certain stereotypes, but other do not based on their natures.