Commensalism is an interaction between two different organisms in which one is benefited and the other is neither benefited nor harmed. On the other hand, amensalism is an interaction between two organisms in which one is always harmed and the other is neither harmed nor benefitted.
Example of commensalism - Goby fish live on other sea animals, changing color to blend in with the host, thus gaining protection from predators
Example of Amensalism - It includes the shading out of one plant by a taller and wider one and the inhibition of one plant by the secretions of another