A technical reply:
World Age affects plot types: flat land, hills, mountains. Older world = flatter world.
Temperature affects terrain types: grass, plains, desert, tundra, snow. Hotter = more desert less tundra.
Rainfall affects feature types: forest, jungle, marsh, oasis, etc. More rain = more foliage.
Sea Level affects percentage of the world that is land vs sea. Higher sea levels = less dry land.
Resources affects resource quantity: for military resources, this affects the number of units per tile; for economic resources, this affects total number of resource tiles in play (and in some cases, at start locations).