|This page in a nutshell: Wikipedia is always bound to change|
An article. A featured article. A bunch of articles. A category. A template. A project page. A guideline. A policy. An editable source. As you see, they are all a certain way when you take a look at them. But are they really meant to stay that way forever?
Fact is, on Wikipedia, nothing is in stone. Not once. Not ever.
On Wikipedia, so many changes occur every second, that if you take a look at the recent changes log (a special page that is uneditable to most), and then check back a few seconds later, you may not recognize anything on the list from your earlier visit.
How easy is it for Wikipedia to change?
If you look at the top of each page, there is a tab with the word "edit." This one little thing tells it all. Any pages can be edited. Of course, some pages may lack this when they can only be edited by certain groups that you do not belong to. Even so, there is someone out there who does have the ability to make changes to that page.
I can make changes. Now what?
You are an editor. Everyone who has a computer with internet access is an editor. Being an editor is not a special title. It is what belongs to all users, registered or not. Even those without a username can make changes to most existing articles and start discussions. And once you become an autoconfirmed user, which you can be in just a few short days, you are able to edit all but a minute number of pages.
So go ahead. Edit. But edit wisely. Think very carefully about what you do. You can edit. But so can everyone else out there. And your edits are subject to scrutiny from others. Pages can be watched. Most existing pages are watched by at least a few editors. And when a change is made, those watching that page will review the change to see whether or not it is a good one. Is this a good change.
It is a good idea that before you go crazy editing for the first time that you get familiar with at least the most basic of Wikipedia's guidelines so your edits are good ones, and you become a well-respected editor.
If you are a veteran editor, this information applies to you too. It is easy to take what you read for granted and accept it as the status quo. But if you disagree with the way it is, you can be the one to change it. The changes you make can range from adding information to an article, adding sources that are needed, reorganizing the information, merging and splitting articles, creating new categories, templates, etc. If you feel something isn't right, you can go ahead and do something about it. No permission is needed.
So, some content is missing
You come to look up information on something. It is something you feel belongs in an encyclopedia. But it is not here on Wikipedia. So what do you do now? Huh?
Remember, there's a first for everything. So if no one has included a category of something within Wikipedia before, you can be the one who introduces it. Read Your First Article before you rush into creating articles just because you can.
Wikipedia can change when you're not looking
One day, you read an article on something. You take it as fact. Several months, weeks, or days later, you come back to the same article. Now it says something totally different. In fact, in some cases, it may not be there at all.
There are many reasons for an article to change. Some articles have dated information that constantly requires updates. Part of the beauty of the Wiki system is that information can be updated moments after it changes. Sometimes, an editor will discover a better way to write something. Or sometimes, the article will just be expanded as more information that previously was not included was added; this often results in more articles being created.
Policies and guidelines can change
The way Wikipedia is run is dictated by quite a large number of policy and guideline pages, found in project namespace. They cover everything from the behavior expected from all editors, to whether or not something is worthy of inclusion, to the styles in which various content should be written. Policies and guidelines have been determined through the power of consensus, and are constantly cited as editors try to reach consensus on other issues.
But if you look at any policy or guideline page, you may notice the edit tab is there too. It is just as open to editing as any article. Few of these pages have full protection, and many are free from semi-protection, allowing literally anyone to edit them.
Now that you are aware of this, you may be tempted to go ahead and make all the changes you wish to all the policy and guideline pages to suit your own beliefs. But it is important to be aware that as their contents were decided through consensus, it usually takes consensus to make any changes to them.
Yes, it is easy to click the edit tab, write in whatever you would like, and then save your changes to a policy or guideline page. But the likelihood that these changes will be reverted is extremely high even for veteran editors who make such changes to these pages without a discussion. If you have a great idea on how a policy or guideline should change, it is best to start a discussion on that page's talk page. Or, if no policy/guideline pages cover the topic you wish, you could create a new project page called a proposal.
You also have the option of writing an essay. Essays contain the advice, opinions, ideas, and policy/guideline interpretations of one or more editors. There are hundreds of essays on Wikipedia. In fact, this page itself is an essay. Unlike policy and guideline pages, they do not require consensus to be written. As for being modified, you guessed it.
You may or may not be interested in making any changes to the policies and guidelines. Even so, that does not mean it isn't happening. One day, you may read what some of them are. You may follow them as if they were that, only to check back some time later and find they have changed. If so, they have probably changed for a good reason too.
Discussion is not standing policy
A discussion is held. An agreement was made between all the participants. A conclusion was reached, and changes were made to the related page as a result. Now, the results can be permanently applied everywhere throughout Wikipedia.
Fact is, consensus can change. Many factors both inside of Wikipedia and in the outside world can cause members of the Wikipedia to change their minds on an issue. Subjects that at one time were not notable can become notable, and those once thought to be notable can later be found not to be. A certain behavior among editors can be allowed one day, then disallowed the next. There is always room for change.
Each page in every namespace has an attached talk page where discussions are held on how to best write and maintain that page. These discussions are particularly necessary when two or more editors cannot agree on how the page should be displayed. Each situation from a discussion is determined on a case-by-case basis. That is their purpose. Their outcomes do not dictate what goes on elsewhere.
The same is true whenever a discussion is held for a deletion. Each such discussion is determined individually, and its outcome does not automatically mean others will be handled identically.