The topography of Madagascar is fairly straightforward. This is an island that is low (as all islands are) on the perimeter but which has highlands in the middle.
The east coast of Madagascar is made up of a very narrow strip of lowlands. The lowlands are made up mainly of soil that has eroded from the hills above.
The highlands themselves are more complex topographically. There are some points that are quite high, with the highest point being almost 9500 feet above sea level. Most of the area, however, is between 2600 and 6000 feet in elevation. Parts of the highland are eroded hills that can be farmed. Other parts are rockier and less usable for humans. There is a rift valley in this area.
The west side of the island is wider than the east side. It is on this side that the major rivers on the island flow from the highlands to the sea. This side of the island has a coast that is more indented, with much more in the way of harbors than the east side has.