The word "swamp" refers to an area of land, while the word "bayou" refers to a body of water. Swamps and bayous are often found in similar areas or adjacent to one another, but the words refer to different aspects of their shared landscape.
A swamp is defined as a tract of wet, spongy land that contains certain types of trees and other vegetation that are unfit for cultivation. A bayou is defined as the inlet or outlet of a lake, river or other body of water that's usually sluggish or stagnant or completely still. Bayous are common in the Gulf Coast region of the southern United States.