Let's start with the letter E. Notice, it has one line of symmetry and that line is horizontal. If we were to reflect (or fold) the E over the blue line, which is also called the line of reflection or the line of symmetry, a mirror, or identical image of it would appear on the other side (shown in red).

The letter H has two lines of symmetry, a horizontal line and a vertical line. Again, think of folding the H along either one of these lines of symmetry and you will obtain the same image on the other side of the line. That is, the green image will match the red image.

The letter O also has two lines of symmetry, just like the letter H. If the O had been a perfect circle, it would have had an infinite number of lines of symmetry, all passing through the center of the circle. However, since the O in this font is oblong (taller than it is wide), it only has two lines of symmetry.

Now, let's look at the letter N. You might think there is a line of symmetry, maybe diagonally or horizontally. But, as you can see, when we try to reflect the outlined green piece of the N over what we might think is a symmetry line, we do not obtain a mirror image. That iss the reflection image (shown in red) does not match up with the pink N. Thus, the letter N has no lines of symmetry.