1. Graphical Scale: This is where a line is segmented (usually with black and white blocks) to denote various distances on the map.

2. Verbal Scale: Uses words to describe the ratio between distance on the map and actual distance on the ground. "1 inch on the map is 10 miles" Ex: 1 inch = 10 miles

3. Fractional Scale: Uses a representative fraction to describe the ratio between the map and the real world for any particular unit of measurement. Ex. 1:100000

The fractional scale commonly requires unit conversion. If the fractional scale is 1:100000, and the distance between two points on the map is 2 inches, then the distance between those points in the real world is 200000 inches (2 x 100000 - from the fractional scale), but this measurement isn't too useful. You wouldn't tell someone to turn left and continue 200000 inches to reach their destination!

Hope this helps!