The answer to all your questions : http://justfuckinggoogleit.com/ Damn filtered x.x Answers just a FF Add-on which allows you to use scripts to perform various tasks. Just google it.
Thanks. Time for another question though. What do you do with greasemonkey, y'know, on neopets or whatever?
Greasemonkey is a firefox add-on that allows you to run bits of javascript on a page. Greasemonkey scripts can do various things though, from play games to change site themes, etc. Some even autobuy(be careful, some are malicious though). neopets-cheats-f80/useful-neopets-greasemonkey-scripts-t18253.html is a list of useful neopets greasemonkey scripts. http://userscripts.org/ is a site with LOTS of greasemonkey scripts, for everything from neopets to youtube. Just use the search feature on the site and you'll find neopets scripts, youtube scripts, myspace scripts, etc. If you want neopets though, just go to the thread link above.
Javascript is a scripting language. It allows websites to dynamically change their content. In other words, javascript allows web developers to change the content on their site in response to user input. For example: When you click on a smiley when making a post here on the forums, Javascript is what puts the smiley in the text box. Greasemonkey is a program that allows the user to run javascript that the original web developer did not put into the site. This user-injected javascript can automatically manipulate the web page to do things like autobuy or autoplay.
Since I have a mac, auto's have been really hard to come by for online games such as neopets and runescape. Recently though, I found greasemonkey and it actually works on macs! Still getting the hang of it, but so far so good! Greasemonkey is very useful for non-techie mac owners.