Bookmarklets are JavaScript programs stored as bookmarks. The term is a portmanteau of the words bookmark and applet. Bookmarklets are possible because the javascript URI scheme allows JavaScript programs to be stored as URIs and URIs can be stored in bookmarks. Bookmarklets have access to the current page, which they may inspect and change. As such, they can be simple "one-click" tools which add functionality to the browser. Bookmarklets are typically installed by navigating to a web page that links to a javascript URI, right-clicking the link, and clicking the bookmark option.
Web developer Steve Kangas got the idea from the Netscape JavaScript Guide,[8] and coined the term "bookmarklets" in 1998.
How to use Bookmarklets? Just drag it to your Bookmarks, Favorites, or whatever you call them!
How to find them? Just Google it...