On a map, reality has been reduced by the card makers. We then say: 'the cards are drawn to scale'.
Above the maps in the Grote Bosatlas is the scale (schaal) and a scale bar (schaalstok).
For example, the map of the Netherlands contains 1:25,000 (pronounced: 1 in 25 thousand). This means: 1 cm on the map is actually 25000 cm. Of those centimeters you make kilometers: 25,000 cm = 0.25 km.
Tip: If you have to make centimeters of kilometers, you just get a handful of (five) zeros! Example: 1: 1200,000 means: 1 centimeter on the map is actually 1200,000 centimeters. From centimeter to kilometer you go in five steps: cm - dm - m - dam - hm - km. Every step goes a zero, five in total. You therefore reach 12 km.
Scale use: https://www.youtube.com/watch?v=oCPf-JURH44