If you are new to the universe of Warhammer 40,000, it can all seem so overwhelming. Space Marines, the God-Emperor, Orks, the Aeldari, the Horus Heresy...it is downright incomprehensible for someone who has never been introduced to these concepts before.
For the true novice, the Warhammer 40,000 Wiki can serve as a real resource to help bring you up to speed on what the hobby is all about. This page will provide a few short suggestions about how to navigate the wiki so that you can gain a basic understanding of a fictional universe nearly as detailed as our own.
First, to get a basic understanding of what is happening in the universe of Warhammer 40,000, you should read the Timeline of the Warhammer 40,000 Universe and its related page, the Imperial Calendar, which will fully explain Warhammer 40,000's unique (and confusing) system of recording dates.
This will provide you with a broad overview of all the major events that have defined the Warhammer 40,000 universe and the major factions that contend with one another within its confines.
Next, you should look at the Age of the Imperium which will provide you with a more in-depth look at the primary Human faction in the universe and the faction whose perspective (by necessity, since we are all Human) dominates the published information here on the wiki.
Once you have gained this broad view of the immensity that is Warhammer 40,000, you should continue your exploration by investigating each of the major factions, most likely starting with the Imperium of Man, the Human interstellar government that is currently the dominant faction in the Milky Way Galaxy of the 41st Millennium AD.
The Imperium of Man wiki page is what we call a "portal page," whose categories, listed at the bottom of the page in blue text, can lead you out to dozens of other pages which will allow you to gain a better understanding of more specialised topics.
This structure is repeated for each of the galaxy's major factions on their relevant portal page. So if you want to start an exploration of the T'au, start with the T'au page and then use its bottom-of-the-page categories to explore more specialised T'au topics, and so on for each of the other major factions listed on the main (front) page of the wiki.
Because of the enormous capacity for networked information provided by a wiki structure, you will soon discover that every page can lead you along another route of knowledge and exploration of the Warhammer 40,000 universe that you didn't expect.
I hope this short guide is useful for those seeking to navigate our ever-expanding database for the first time, and I envy the thrill of discovery you are about to enjoy as you explore the grim dark future of Warhammer 40,000!
--Montonius, Lead Administrator, Warhammer 40,000 Wiki, January 23, 013.M3 (2013 AD)