HTML is the basic building blocks of a web page. It is represented on a page using "tags", which are left and right arrows"<>". The tags are both, open and closed. In between those tags is where you would insert your content for that page.
I like to describe a webpage like a House:
You have the outside, from which all of the world notices: "Index, or landing page."
There are separate rooms within your home that contains different things that pertain to who you are and what you home has: "About Us, featured pages, pictures, phones and such which is a means of "contact"".
There are is a way your house looks, such as: the color of the walls, the structure of the rooms, style of flooring, ect. "CSS, cascading style sheet, which determine the styling of your site/home".
Your house has functionality, such as: Lights that turn on and off, water that you can turn on and off, doors that you can open, sounds that things make, the illumination of room. Your action will cause a reaction in the room. Thats what java-based programming does, gives your site life!!
This is just something very basic, and I will go into more detail is later blogs and HTML based features.