A talk page is a Wikipedia page containing discussion about the contents of the main page of which it is a subpage. For example, most political figures, such as Bill Clinton, have their own talk page (Bill Clinton/Talk). Extremely controversial topics almost invariably have talk pages; e.g., Abortion/Talk, Capitalism/Talk, Socialism/Talk, Jesus Christ/Talk.
On Wikipedia, the primary purpose of a talk page (also referred to as a
/Talk page) is to help to improve the contents of the main page, from an encyclopedic point of view. Questions, challenges, excised text (due to truly egregious confusion or bias, for example), arguments relevant to changing the text, and commentary on the main page is all fair play.
It seems safe to say that most Wikipedians generally oppose the use of talk pages just for the purpose of partisan talk about the main subject. It also seems safe to say that most Wikipedians would regard partisan wrangling as fine, if in some fairly clear way it will lead to the improvement of the article. Some other Wikipedians disagree, believing that we should all feel free to write whatever we like on the topic of the page to which the talk page is appended.
Generally speaking, when a talk page's contents become extremely large, particularly if they are outdated, they should be refactored. See editing policy.