I have come across these two terms which are used interchangeably in many contexts.
Basically, a moderator (M) is a factor that impacts on the relationship between X and Y. Moderation analysis is usually done using a regression model. For example, gender (M) can affect the relationship between "product research" (X) and "product purchase" (Y).
In interaction, X1 and X2 interact to influence Y. The same example here is that "product research" (X1) is affected by "gender" (X2) and together they affect "product purchase" (Y).
I can see that in moderation, M affects the X-Y relationship but in interaction, M (which is gender in this case) affects the other IV.
Question: If the aim of my project is to see how gender affects the relationship between X and Y, should I use moderation or interaction?
Note: My project is about the correlation between X and Y, not causal relationship between X and Y.