Titles are how you identify an anime - there are many different kinds, both official ones and common ones as well as abbreviations. No anime can have have the exact same title as another. The Main Title (the Japanese transcription title per default settings) is listed at the very top of each anime entry, and at the top of the details table next to the image. The rest of the titles are listed with language and title type details. Anyone can add a title to any anime, with the restriction that if there already is an anime with that exact same title, it won't work; please use the search function to check for overlaps. Anyone can request that a title be edited or removed, but it will have to be approved by a mod, so state a good reason for why you wish it to be edited or removed. More Info...
Official Title (Japanese, Kanji)
Anime title: Hagane no Renkinjutsushi Official Japanese Kanji title: 鋼の練金術師
Official Title (English)
Check the official English page if it's licensed.
Anime title: Hagane no Renkinjutsushi Official English title: Fullmetal Alchemist
Official Title (Language)
Meant for official titles in other languages. This title should be the title it is sold/aired under in the regions where they use the specified language; if it is sold/aired under more than one name in a language, use Synonyms/Aliases for that.
For anything not official, which is widely used, or if it is sold/aired under more than one name, set them as synonyms/aliases.
Anime title: Hagane no Renkinjutsushi English Synonym: Full Metal Alchemist
A shortened version of the title.
Anime title: Hagane no Renkinjutsushi Shorttitle: FMA
In order to add a title to an anime, you need to go to the 'contributions' tab of an anime entry and click the 'add/edit titles' link there. This will lead you to the "Add/Edit Names for ..." page, where you can see (and request removal of) all the titles and which language they are in, that are currently added to the anime, as well as a tab where a text field and a few lists let you enter a new title and select what kind of title it is and which language it is in.
If an anime is or has been sold/aired in your language with a specific title, go ahead and add that title as 'Official Title' for your language. If you see a title that is clearly wrong under these contitions, please request removal or change the type of that title, stating your reasoning for the change so a mod can approve. If an anime has never been sold or aired in your language, there is no reason it should have a title in it, so please don't add one.
One thing AniDB relies on are its users from different regions, who can check and verify titles in different languages. If you would like to help out with this effort for languages you know, please don't hesitate to contact us on irc://irc.synirc.net/anidb. You can see a list of which languages already have people who can verify them on the staff page.