WEEK 43: GETTING DOWN WITH THE MARKUP
If you want to edit Wikipedia effectively, you're going to have to learn "wiki markup", also sometimes called "wikicode".
In programming contexts, the phrase "markup language" suggests a simplified language, like HTML. That's exactly what Wikipedia's markup is: similar to HTML, in fact sharing some elements with it, and even easier to pick up.
Its basic formatting is different from HTML, though. Wikipedia markup uses equal signs (=) to create section headings, square brackets to make links (), and single quotation marks (') to create text formatting. Combining these in different numbers, with a few additional markup elements, produces most of what you read on Wikipedia. For specific examples, see the Wikipedia Cheatsheet.
These days, the optional VisualEditor hides most markup elements from new editors. It's more streamlined, but not as powerful. Even if you're inclined to use the VisualEditor more often, it's worth taking the time to learn the markup basics.