Wikipedia page formatting is done with Wikitext, so you don't need to learn HTML.
Wikitext or Wiki markup
Writing for Wikipedia articles is a bit different from writing on a standard word processor. Instead of a strict "what you see is what you get" approach (WYSIWYG), wiki uses a simple built-in MediaWiki markup language designed for ease of editing. The approach is similar writing HTML for web pages, but the codes are much simpler.
Bold and italics
The most commonly used wiki tags are bold and italics. Bolding and italicizing is done by surrounding a word or phrase with multiple apostrophes ('):
''italics'' appears as italics. (2 apostrophes on both sides)
'''bold''' appears as bold. (3 apostrophes on both sides)
'''''bolded italics''''' appears as bolded italics. (5 apostrophes on both sides)
It is a Wikipedia convention to boldeeer the subject of an article when it is first mentioned in the article. For example, the article Klinefelter's syndrome starts:
Another Wikipedia convention is to italicize book, movie and computer/video game titles. If the first mention of the subject of an article is also a book or movie title then bold italics is used. For example, the article The Lord of the Rings starts:
Headings and subheadings are an easy way to improve the organization of an article. If you can see two or more distinct topics being discussed, you can break up the article by inserting a heading for each section.
Headings can be created like this:
==Top level heading== (2 equals signs)
===Subheading=== (3 equals signs)
====Another level down==== (4 equals signs)
If an article has at least four headings, a table of contents will automatically be generated. Try creating a heading in this page's sandbox. It will be added automatically to the table of contents for the page, assuming three others already exist.