Final answer:
The brown lines on a topographic map represent contour lines, which indicate the elevation of the terrain.
Step-by-step explanation:
The brown lines on a topographic map represent elevation. These lines are known as contour lines and are used to illustrate the shape and height of the terrain.
Mapping these lines requires understanding that each line corresponds to a particular elevation level above sea level. The closer these contour lines are, the steeper the terrain is at that location.
When creating a topographic map, these elevation lines provide valuable information about the Earth's surface features such as hills, valleys, and slopes, which is crucial for various planning and recreational activities.