All literate people write. But why do some people become or aspire to become authors?
Some people write for pleasure, some write for fame, to get their name up in print and some write to earn their daily bread.
For some, writing is a pastime, a hobby just like gardening, games and other such pursuits. These are the people who write to express their feelings and hope to derive satisfaction out of such writing. These types of people are more likely to write poems and stories aimed primary at satisfying themselves with little regards to literary rules and conventions and marketability of their literary works.
The second category of writers, who write for fame or recognition are the ones who write for journals and other avenues of publishing. They are most likely to publish a novel or if the pursuit ends up in failure, try their hands at self publication. They are most likely to pay up to see their name appear in print.
The third category of writers are writers who earn to make their living, and this definition includes journalists, content writers, ghost writers and the like. They are primarily concerned about how much their writing with earn for them, even if it appears in the credit of another person;s name.