Help:Introduction to editing with Wiki Markup/1
Editing pages
Activate editing mode
Formatting
Keeping it tidy
Wikilinks
Connect pages to each other
Saving your changes
Publishing
Creating new articles
Building a page from scratch
Summary
Review of what you've learned
A note about editing on mobile devices: Most Wikipedians prefer to edit from a computer, as the editing interface works better there. You can edit from a mobile device, though. See this page for more information.

Wikipedia is formatted using its own language called Wiki markup, also called Wikitext. It's pretty easy to learn the basics.
You have a choice of using one of two editing tools; the "Source Editor" uses wiki markup.

Alternatively, you can use VisualEditor, a newer editing interface that works more like a word processor. While VisualEditor is simpler to use, the Source Editor can be more effective for some tasks. You can easily switch between them while editing, as shown at right.
To view and edit a page using Wiki markup, click Edit source at the top of any page. This will allow you to type text that you want to add, using wiki markup to format the text and to add other elements like images and tables that are explained later in this tutorial.
Wiki markup can initially seem intimidating (especially references) but it actually requires only a few rules to understand and use, and you'll quickly get used to it! You can always test new techniques in your personal "sandbox" page.