Header / Headings
These are standard HTML tags such as <h1> and <h2>. Most search engines give extra weight and importance to text found within these tags. It is also considered good practice to use headings within your website.

HTML
This is an acronym of HyperText Markup Language - it is the primary markup language used to create websites.

Hidden Text
Text on a web page designed to be visible to spiders but not to human visitors Using a text font that is the same (or nearly the same) color as the background color, rendering the text or link invisible or very difficult to read. The same effect can also be achieved by using various HTML tricks.

Homepage / Home page / Home
The main "index" page or navigation hub of a web site. The homepage is not necessarily the first page. Many sites use splash pages to welcome visitors and lead them from there to the homepage. At most search engines you can simply submit your homepage and leave it to the spider to crawl the rest of the site from there.

HTTP
Hypertext Transfer Protocol. HTTP is the most common transfer protocol used to facilitate communication between servers and browsers.

Hyperlink / Link
Clickable content on a web page usually leads to another page, another site or another part of the same page. The clickable content therefore is said to link to the other page / site / part of the same page. Spiders use links to crawl from one page to the next as they index web sites.