Significance
For people of the time the tale represented the relationship between lords and common people, the Clerk at the end of the tale tells the readers that the tale is an allegory representing god and people also so it had religious significance as well. The significance it has nowadays is that you should show more loyalty in a relationship and trust in your partner instead of testing them. This also shows that even though you can be from different social classes you can still love someone.
Irony
When the Marquis sends both of his kids away he tells Griselda that he killed the kids but we know they are alive. This shows dramatic irony. More dramatic irony is when the Marquis brings back his daughter he also tells Griselda that this is his new wife but Griselda doesn't know.