The appearance is different, the taste is different, etc.

Mustard is a leafy vegetable with pinnate leaves, larger leaves, and dark green color. Brassica napus is a root vegetable with smaller leaves that grow on top of tubers and can be green or purple in color.

Mustard greens have a spicy flavor, similar to the spiciness of mustard. The spiciness comes from the capsaicin, isothiocyanate. The flavor of cranberry is relatively mild and not spicy. The taste is crisp and refreshing, with a bit of sweetness, similar to the taste of radish.