Lets start with the top half of a basketball.  
The lines across are one inch apart. It is easy to see this half ball is 5 inches high. That is all the lines on a contour map indicate, height of an object.

Look down , from the top of the ball. This is how the top of a perfectly round mountain would look. It's easy to see how tall the ball is. To find how far it is across this mountain, measure the distance across the lines. There will be a mileage scale in the legend. Compare your measurement with legend scale.

You now know what basketball mountain looks like, let's look at football mountain.

You can see this mountain is longer than tall.

Note the lines, of the top view, are further apart at the ends. The  further apart the lines, the flatter the surface.

 If you were choosing a way to climb this mountain, it would be easier climbing to start from the end. Starting from top or bottom would be shorter distance, but much steeper. The line down the middle indicates the ridge.

Unfortunately mountains on a map aren't that easy. Nature provided gullies, draws, folds, rolls, creeks, ridges, flats, and many other irregularities.
Here are some examples of realistic figures found on contour maps.

The area with the circle shows a creek. Note the creek is much steeper near the top. The heavy line indicates a ridge.

Here are two peaks. The one on the right is much flatter and not as high. Heavy line shows the ridge. Lighter lines indicate smaller ridges . Note the curves. Curves pointing  away the top are ridges. Curves pointing toward from the top are draws.