Layman’s explanations about blogs

Sorry if this is in the wrong area.

I’m trying to understand how blogs work etc and the intricate details of the functions of each thing added. I’ve tried to google the info and wiki it but the stuff is more complicated then I understand. I am trying to get a very basic and as simple of an explanation on:

What tags do:

What is the fuction of a title and how is it used to make your blog searchable:

Besides being the main info of your blog, how is the body key in having your blog searched on the web:

If someone can either answer these questions or direct me to a site that simplifies the explanations I would really appreciate it.