If the file you open is a text file, it will be displayed as plain text. Thus, you can view a text file in the Browser dialog whilst you edit another file with the wordprocessor.
If the file you open is a HTML web page, the page will be rendered according to the HTML coding standard, thus displaying its text, pictures, sounds, links, etc. You will be able to click links (usually indicated as blue underlined text) to move to other HTML web pages. Use the Back and Forward buttons (the arrows shown in Figure 1 below) to move between pages you have already viewed.
You can hold down the Command key (Left-Alt on the PC) and click any character shown in the Browser dialog to get information about it.
This menu item will always be active, since you can load in a new HTML web page at any time.