Once the jQuery library is loaded, a webpage can call any jQuery function supported by the library. Common examples include modifying text, processing form data, moving elements on a page, and performing animations. jQuery can also work with Ajax code and scripting languages, such as PHP and ASP to access data from a database. Since jQuery runs on the client side (rather than the web server), it can update information on a webpage in realtime, without reloading the page. A common example is "autocomplete," in which a search form automatically displays common searches as you type your query. In fact, this is how TechTerms.com provides search suggestions when you type in the search box.
You can read more about jQuery and download the latest library at the official jQuery website.