How do you read the Tour De France route maps?

Question

What do the coloured circles with the numbers inside mean?

Answer 1

They are intermediate points where riders can get points.  The red ones are climbs, the numbers indicate the difficulty of the climb.  Green represents sprint points.

It's a race to the point.  The first few riders across the line get points.

The points are used to determine who wins king of the mountains and sprinters races.

Answer 2

The Green ones are sprints and red are climbs 4 being the lowest HC being the highest