If someone has an idea for developing an article or the way the Wikipedia or its software works, very often a discussion will start on a user's talk page. It might be yours, or it might be another editor's. User talk pages are generally for informal messages between users to bring each other up to date, to give a heads up, to ask for help, to give and respond to messages of thanks. If the case arises, users might receive suggestions from other editors on their talk pages as to how they can improve their editing or interaction, and they might receive notification of administrative actions to their edits, and in the worst-case scenario, official warnings.
User discussions have a habit of being fragmented between the user talk pages, making it extremely difficult for other interested parties to follow. Some users don't want talkback templates plonked on their page, while others editors delete every message (not recommended) as soon as they have read it, and others don't archive their old talk, forcing us to wait for a long page to load before we get to the stuff at the bottom; the same long wait occurs when pressing the preview and save buttons. Having a chat on a user talk page is a bit like two very active members of a pub pool or darts team discussing the rules of the game in the home of one of them. Nobody else is involved, and no minutes are taken, but sooner or later they will want to take these matters up with the other players, in a bigger room, such as in the pub. Thus, a discussion that involves more than two editors, or one which could benefit from the input from more people, should continue as soon as possible somewhere more convenient. Wikipedia has those places.
As soon as the talk seems to be centred on a specific article, policy, or template, etc., the discussion should move over to the topic's talk page. Many regular editors will have that talk page on their watch list, while visitors to the encyclopedia often check out an article's talk page. They might have something useful to say or suggest, but they will not be aware if it has already been discussed somewhere else by a couple of other editors. The article talk page also already has a lot of useful information on it such as project banners, mentions of previous deletion discussions, archives, and attributions to other Wikimedia whose contents have been used. It's the No.1 place for collaboration on articles, and it's where the Good Article reviews take place.
It's important, however, to remember that a Wiki is not quite the same thing as an Internet forum. Although part of the fun of working here is the sense of belonging to a community, just like an Internet forum in many ways, but one in which building an encyclopedia is the sole purpose. For example, there are people who go to the pub just for a drink and a general chat with their mates, while some go with the prime intention of playing pool or darts and organising matches, and having a drink and a bite to eat while they are doing it. An article talk page is even tighter though. Not only do we not talk about the editors, we don't even have a general discussion about the subject; we only discuss the content of the article about the subject - what goes in, what gets removed, and how it should be presented. In some cases, if the discussion moves towards things that would affect not only that article, but other articles of the same kind, again the discussion could benefit from the input from more people, and should also continue as soon as possible somewhere more central. There are venues for that too.
For almost every kind of article, there is a group of editors who have got together to keep track of what's happening on those pages. They've also designed a set of pages around a Wikipedia project. The project pages are full of tips and tricks about writing and improving those articles, and project members also gnome around improving new pages and adding stuff other page creators have left out, especially things like infoboxes, references, stub templates, and categories, and listing articles that need attention. These projects also have a project talk page, and that's the place to bring a discussion to if is going to have site-wide outcome for the articles of that kind.
It may happen of course that the subject becomes so complex that it needs splitting off in to separate groups again or task forces. They will naturally go off and find a corner where they can work together. They will develop yet another talk page for that, but they will probably report back to the main project talk page with their findings. Splitting is fine, as long as it's not splitting hairs.
Basically therefore, although the Wikipedia exists in cyber space, it's organised very much the same way as many collaborative projects in real life. However, it's not a pub after all, and we are all here on the same mission, although some people will try to cheat, sneak in, and try to get a free beer. There are even some poor souls who write graffiti on the walls or break the furniture - here we call them vandals, and there are a few loud mouths too! There are some rules about talk pages and how we communicate on Wikipedia, and knowing where and how to talk about things keeps the conversations on track and prevents editors being blocked for saying the wrong things!
Many new editors just jump in and start editing articles and creating stubs without realising what a huge system of help and support we have here. They sometimes make terrible mistakes in good faith – we all did when we first started here! However, usually no real harm is done and everything can be put right. Do follow the links in this essay for more information, and if you really get stuck, you can either stick that famous {{helpme}} template on your talk page or you can go to one of these places, but please don't post your request in several places at once: