Plains
Plains are areas of level land, generally at a low elevation.  Examples include the Eurasian Plains and the Russian Steppes. Plains generally have fertile soil and are attractive to settlement as they are easy to reach, provide good road building, and have good farmland.  The negative aspects of plains as a geographic feature are that they are hard to defend as they are easy to reach.  Plains also provide no natural protection from the elements.

Plateaus
A plateau is an area of flat or slightly hilly terrain at a high elevation. An example of a plateau is the Deccan Plateau in India.  Plateaus generally offer the same advantages and disadvantages of plains, depending upon the elevation. A higher elevation plateau may offer some protection from invasion due to a more difficult route.  But, the elevation also has disadvantages.  In India, the greatest problem of living on the plateau is water.  Most rivers and streams flow from a higher to lower elevation, so this denies the Deccan Plateau much needed water.  Without water, settlement is difficult.