What is cultural diffusion and what are some causes of it?

Cultural diffusion is when another culture benefits from another by trade or some sort of partnership. Two empires might like to combine their skills and rule as one so that would be cultural diffusion.

Cultural diffusion is the separation of culture from a central point. an example is the Irish potato famine, many Irish people had to leave their home and moved to the U.S. bringing their culture with them and exposing it to others.

Pretty much anything that causes people to leave their home and move somewhere else is a cause of cultural diffusion.