Everything you see on a browser is a combination of markup (text), style (design), and scripts (interactivity). The markup language dictates the architecture of page, with a focus on its text content (although not exclusively).
Hypertext Markup Language (HTML or HTM)
The first and most well-known of internet languages, HTML functions as the foundation and structure of a page's content. After it is set, other aspects can be embedded or attached to that page, like stylesheets or scripts.
- Most widely-used web language.
- Standardized element and tagging system.
- Is used to render content and page structure.
- Consistent version changes and updates require extended education.
- Quality of HTML usage is varied, meaning sites may not always work cross-browser or cross-device.
Extensible Markup Language (XML)
A compliment to HTML, XML describes document nodes, whereas HTML displays document nodes. Its major usage today is in the technologies like those utilized by Gmail that allow specific elements to update without having to refresh the entire page.
- Stored in plain-text format, which simplifies data sharing.
- Eases data transport and availability.
- Allows for upgrading without losing data.
- Does not “do” or render anything, just provides tagged information.
- No pre-defined tags; author must define and structure individually.
Extensible Hypertext Markup Language (XHTML)
Essentially a bridge between HTML and XML, XHTML combines the best of both in an attempt to correct some lenient behaviors of HTML; in particular, those that cause problems on mobile devices. While computer browsers can correct some “bad” HTML, smaller devices often lack the resources to perform these operations.
- Almost identical to HTML.
- Usage ensures that documents are marked-up correctly.
- Strict code requirements make it less vulnerable to future changes - longer to write, but easier to maintain.
- XHTML documents must meet more rigorous standards that HTML to function properly.
- Because it is more precise, it is more time-consuming to write.