HTML:
• HTML stands for HyperText Markup Language and is the standard markup language for creating web pages.
• HTML is not case sensitive, meaning that it does not require the use of uppercase or lowercase letters.
• HTML elements are written using tags, which are enclosed in angle brackets.
• HTML is a static language, meaning that the code does not change when the page is rendered.

Example:

Welcome to my Web Page!

This is my first web page.

XHTML:
• XHTML stands for eXtensible HyperText Markup Language and is a stricter version of HTML.
• XHTML is case sensitive, meaning that it requires the use of uppercase or lowercase letters.
• XHTML elements must be written using tags, which are enclosed in angle brackets.
• XHTML is a dynamic language, meaning that the code can change when the page is rendered.

Example:

Welcome to my Web Page!

This is my first web page.