A ridge has a linear, or long shape. It is like a hill, but instead of being somewhat rounded, is elongated. Scan the points on this map and you see the z values increase from the upper left corner down toward the middle, and from the lower right corner up toward the middle. You see points with z values in the 1400 range in a linear trend from lower left to upper right:
For this example, the contours are fairly straight, indicating that this ridge is long and linear, which is common, at least locally:
Of course, some ridges are "curved" across a larger map area.