Verdana is probably already installed on your computer. Not surprisingly, these fonts are termed fixed width and variable width respectively. Start up you word processor. Now select the two lines of characters and set the font to Courier or Courier New. Notice that both lines are now the same length.
Courier is a fixed-width font.
It should be no surprise that variable-width fonts look more natural and are thus easier to read. As an exercise go through the fonts on your computer and find five variable-width, serif fonts that you like the look of. Choose among these for the body copy of your documents. Use these for your headings, captions, headers and footers. Armed with these simple ways of classifying fonts, you should now have an easy time of choosing suitable fonts for all occasions.