Disambiguation pages are pages with titles that might refer to more than one thing, as described in Help:Disambiguation.

For example, "Megatron" could refer to several different characters all with the same name. The Megatron page should redirect to a disambiguation page so that somebody who searches for it will be given a list of all articles with that title such as Megatron (G1), Megatron (BW), and Megatron (Armada).

When you write a disambiguation page, you can mark it by including the "disambig" template. Simply write {{disambig}} at the bottom of the page to include the template and automatically categorize the page as a disambiguation page.