A cookie is just a very small file that a website saves on your computer (or smartphone, tablet, etc.), in order to keep track of information that it uses when you visit the site. Cookies are stored in one of the directories that a browser uses for saving website data. Many cookies simply contain data that allows the website to recognize you computer, and to display itself based on your preferences, or on your previous actions at the site. Other cookies allow websites to do such things as keep an accurate count of the number of unique visitors to each page. Cookies are text files; they do not contain binary code, and cannot run like programs on your computer.
Each cookie includes its own expiration date. Many cookies are set to expire when you close your browser. These cookies are known as 'session cookies,' and contain information that is only used while you are browsing the site. Other cookies, called 'persistent cookies', have longer expiration dates (measured in months or years), and contain data that may be used from one site visit to the next. You can find out more about cookies and how they work at http://allaboutcookies.org, and at the Wikipedia entry for HTTP cookies, http://en.wikipedia.org/wiki/HTTP_cookie.
Basic cookie functions allow us to keep track of how our site should be displayed in your browser, which of our site's pages you have recently visited, authentication settings, country and language selections, and similar information. This makes it possible for you to view our website according to your preferences, without having to re-enter those preferences each time that you come to our site.
We also collect statistical information so that we can understand how people use our site, and how we can improve it. When we do this, we aren't concerned with what any one person does, but with the overall numbers. We want to know how many people viewed a specific page or document, how long they spent there on the average, what pages they came from or went to, what things people clicked on, and which ones they ignored. This kind of information tells us which items at our site are the most important to our users, which items work the way that we think they should, and which ones are not doing what they should be doing. Cookies allow us to count the number of individual users who have done something, as opposed to one user doing the same thing repeatedly.
Your browser will typically include options or add-ons which allow you to disable or remove cookies for specific sites. You can use those options to remove or disable our cookies. This is something that you might want to do if, for example, you are accessing our site from a computer that other people use (i.e., on a public computer at a library, school, or Internet cafe), and where you cannot control the security settings. Be aware that if you do disable cookies for our website, it will not remember your preferences and settings the next time that you visit, and you will need to re-enter them.
If you are accessing our site from a computer or other device which only you or other family members use, it is generally much better to leave our cookies as-is, and not disable or remove them.