Enter your email address in the box provided. If you want a link to have something other than your email address, put that alternative text in that box. Then click on the Obfuscate button and copy and paste the version you want into your page. Use the version in box 1 for most pages. The other versions are for other less common uses, like giving the email address in normal text instead of a link.
You can enter an initial subject and email message text in those boxes if you like. Some email clients will ignore these values.
The javascript versions will only work if the viewer of your page has javascript turned on. Most people do. The non-javascript versions still provide effective protection today but are more likely to become ineffective as spammers adapt to the technique. Javascript is likely to remain effective against harvesting for as far in the future as can be predicted today.
Your email address is never sent anywhere when you use this page. If you prefer, you can save it to your hard drive and use it from there without an internet connection.