Words are normally dark on a light background.
Highlighting turns backgrounds into a different color. Like this white sentence with a dark background.
Here is how to highlight:
  1. Place the tip of the arrow in front of the word or words to highlight.
  2. Hold the left mouse button down.
  3. Drag the arrow across the text.
  4. When background behind the text is a different color, the text is highlighted.
Try highlighting this word. ----------------------------> Hey,
Try highlighting this sentence. ----------------------------> Hey, I did it!
Try highlighting this paragraph. ---------------------------->
You will need to drag the arrow down as well as across.
Hey, I did it. I highlighted this whole paragraph.
But why? What's the point of highlighting?

For the answer, click 31