Wikipedia articles are formatted according to the Manual of Style. It sets standards for attributes like link formatting (list external links in their own section at the bottom of an article), capitalization (do not capitalize all words in section headings), punctuation (remember the serial comma), sections (an informative lead section is important), and many other stylistic details. There are separate guidelines for biographies, citations, titles, dates and numbers, and proper names. The naming conventions set standards for titling articles, such as do not capitalize all words and use the singular form wherever possible. You don't have to use all these rules and recommendations when you update an article, but please do not be alarmed if others edit your writing accordingly.
Read more: Wikipedia:Manual of Style