Bookmarklet

Definition
A bookmarklet (a portmanteau of the terms "bookmark" and "applet") is a bookmark stored in a web browser that contains JavaScript commands to extend the browser's functionality. For instance, a bookmarklet might allow the user to select text on a page, click the bookmarklet, and be presented with a search engine result page for the search term selected.

Overview
Bookmarklets are unobtrusive scripts stored as the URL of a bookmark in a web browser or as a hyperlink on a web page.