A web page is a text file that contains text and HTML tags.
HTML tags are simple instructions for a web browser.
A web browser is a program like Internet Explorer or Firefox.
It interprets these HTML tags to display your web page.

Here is the HTML used to show the above four lines in a browser:
<p>
   A <strong>web page</strong> is a text file that contains text and HTML tags.
   <br />
   <strong>HTML tags</strong> are simple instructions for a web browser.
   <br />
   A <strong>web browser</strong> is a program like Internet Explorer or Firefox.
   <br />
   It interprets these HTML tags to display your web page.
</p>

If you run an html file on your computer it will open in a browser. The address will point to the file on your computer. In order to make it available to others you need to place it on a web server. When it is run from there the address will point to the file on the web server.