Sometimes a word means more than one thing, so you might want the same title for two different pages.
To solve this, we disambiguate.
Wikipedia grows very fast because making links is quite simple and natural. When you type in a window for editing, put two brackets on each side of the word (like this: [[Mercury]]) and you will get Mercury. If you do this to a word you have made it a link.
There are many things called Mercury. Some of these are:
Solving this ambiguity can be done in several ways:
"Sub-topic" disambiguation: many small articles of just a paragraph or so each can exist together on a single page, separated by headings. However, as each section grows, there comes a time when each article must have its own page.
"Equal" disambiguation: all articles are moved to distinct names, and the "Mercury" page becomes a disambiguation page: a simple list that points to those specific articles, perhaps explaining the differences among them.
"Primary topic" disambiguation: if one meaning is clearly predominant, it remains at "Mercury", the general title. The top of the article is given links to the other meanings, or if there are many, to a page named "Mercury (disambiguation)". For example: the page Bat has a link at the top to a page named "Bat (disambiguation)" which lists other things named bat. The page Cream has a link to the page Cream (band) at the top.
Making a disambiguation involves four steps:
appropriate (and distinct) titles are chosen for the specific topics
the disambiguation page is written
any existing links to the general title are replaced by links to the appropriate specific topics
a link to the new disambiguation page is added to the appropriate list (see "Links to disambiguation pages", below)