A basic HTML document can only be one page. However, you may use JavaScript and CSS to change the displayed content when the user clicks on a link or a tab, giving the illusion of several pages in one (see this example). Another possibility is to have all the text in the same page and choose which part to display according to the URL thanks to PHP (see that example). Google is your friend.
Several pages in a single HTML document
A basic HTML document can only be one page. However, you may use JavaScript and CSS to change the displayed content when the user clicks on a link or a tab, giving the illusion of several pages in one (see this example). Another possibility is to have all the text in the same page and choose which part to display according to the URL thanks to PHP (see that example). Google is your friend.