In brief
HTML code marks a fragment of computer code. Marking it up does not execute the command or guarantee valid syntax.
Useful to know
HTML code marks a fragment of computer code. Marking it up does not execute the command or guarantee valid syntax. [1]
When displaying an HTML example, represent special characters safely so they do not become page markup. For multiple lines, consider pre too; code semantics and whitespace preservation are separate tasks.
Sources
For further detail and to check the information: