An anthro or 'furry' is an anthropomorphic animal-- that is, an animal that has human traits, or a human that has animal traits (ears, tail, fur, etc.)
A fursona is the artist's representation of themself as a furry.
Stemmed from the fact that many furries, furry artists, Therians, or those in other parallel or related groups used animal or anthropomorphic personas. These personas were dinifitive enough to be given their own generalized name: fursonas.
Many young oekaki users start off drawing characters from Disney films or animals in general, therefore when drawing a representation of themselves find an animal easier for them to draw repetitively. It can also serve as an escape from the reality of what they really look like, where the fursona's personality is more akin to how they act online than in real life.
In recent years popular oekaki have distorted the meaning of 'fursona' on oekaki, as furry artists have attempted preaching the origin to young users, and trends have been formed by popular artists that have slowly become a norm or standard.
In failed attempts to make original generic wolf or cat fursonas some artists have gone to extreme lengths to put complex patterns and accessories on their fursona. Common items are piercings, star shapes, moon shapes, stripes, leg warmers, glowsticks and fishnet anythings.
On many oekaki people confuse their fursona with muses, the difference being that your fursona represents yourself, and a muse is a character that expresses things or that you use frequently in varied ways (eg. roleplay and writings). This leads to some people arguing against the girl who's name could be 'WaterPrincessLucy' online but who's fursona is a male, red, fire-breathing dog called Damien.
Fursona whose genders don't match their creator are very rare but a controversial subject for most. Some would liken it to the man who roleplays only female characters or dresses as a bunny girl to his local furry convention.
An animal, it may be made up or real, representing yourself. It is usually the same gender and personality as the creator and may be given exaggerated fur patterns.
It may be portrayed as an anthropomorphic character, giving it human like limbs. Eg, arms and legs of a human.
They are sometimes drawn as sparkledogs, or if it's not a dog or wolf, sparkleanimal. In this case, they are dressed and shown as either emo or gothic and have dark colours, or are colourful and rainbow with bright colours that are apealing to the eyes. Sparkle artists give their sparkle animals big hair that cover the eyes, peircings, and stalkings.