Salmon en Croute means “salmon in a crust” in French. It's salmon and a spinach filling wrapped with puff pastry. Salmon Wellington is the same thing, it just borrows the more familiar word "Wellington" for its name. A traditional Beef Wellington is made with beef tenderloin, a mushroom filling, and parma ham.  It is also wrapped in puff pastry, hence the shared 'Wellington' name.  Salmon Wellington is also called, salmon wrapped in puff pastry.