What does exclamation point stand for in HTML in constructs like DOCTYPE and comments?

Question

I am curious about the syntax of the doctype and comment tags...

Why the exclamation point? What is it called, what does it mean/do?

I have read through the

Answer 1

The ! is used for comments () and to define the DOCTYPE () of the HTML document. The DOCTYPE describe some characteristics of the document such as the root of the XML/XHTML/HTML file (in HTML usually is ), a DTD, a Public Identifier and other subset declarations.