1. XHTML ：
XHTML 代表可扩展超文本标记语言。它可以被认为是 XML 标记语言的一部分，这是因为 XHTML 具有 XML 和 HTML 的特性。 XHTML 是从 XML 和 HTML 扩展而来的。 XHTML 可以被认为是 HTML 的更好版本。
2. HTML :
HTML 是超文本标记语言，是互联网上使用最广泛的语言。 HTML 用于创建网页并将它们从一个链接到另一个。请注意 HTML 不是一种编程语言，它是一种标记语言。我们可以使用不同的其他技术，如 CSS 和 javascript，让 HTML 开发的页面焕然一新。
HTML 和 XHTML 的区别：
| S.No. | HTML | XHTML |
|---|---|---|
| 1. | HTML stands for Hypertext Markup Language. | XHTML stands for Extensible Hypertext Markup Language. |
| 2. | It was developed by Tim Berners-Lee. | It was developed by W3C i.e World Wide Web Consortium. |
| 3. | It was developed in 1991. | It was released in 2000. |
| 4. | It is extended from SGML. | It is extended from XML and HTML. |
| 5. | The format is a document file format. | The format is a markup language. |
| 6. | All tags and attributes are not necessarily to be in lower or upper case. | In this, every tag and attribute should be in lower case. |
| 7. | Doctype is not necessary to write at the top. | Doctype is very necessary to write at the top of the file. |
| 8. | It is not necessary to close the tags in the order they are opened. | It is necessary to close the tags in the order they are opened. |
| 9. | While using the attributes it is not necessary to mention quotes. For e.g. |
While using the attributes it is mandatory to mention quotes. For e.g. |
| 10. | Filename extension used are .html, .htm. | Filename extension are .xhtml, .xht, .xml. |