Most word processors are WYSIWYG-based. While HTML does provide extensive capabilities to control the look of a document, it is NOT WYSIWYG-based.
An HTML tag is a text markup command. Each tag starts with a "less than" symbol and ends with a "greater than" symbol.
The first word in each tag is a command name. Command names are case insensitive. Some tags also contain attributes with assigned values. Attribute values can be case sensitive, so be careful!
Some tags do not require a closure tag, while other tags require a closure tag containing the command name with a leading slash. Tags requiring closure must be properly nested (they cannot overlap).
Examples of HTML elements: