* English walnuts (also called Persian walnuts) are from the species *Juglans regia*. They are the most common type of walnut found in grocery stores. They have a mild, sweet flavor and thin shells.
* Black walnuts are from the species *Juglans nigra*. They have a much stronger, more pungent flavor and a very hard shell. They are often used for flavoring in cooking and baking.
Here's a table summarizing the differences:
| Feature | English Walnut | Black Walnut |
|---------------|----------------|---------------|
| Scientific Name | *Juglans regia* | *Juglans nigra* |
| Shell | Thin | Thick, hard |
| Flavor | Mild, sweet | Strong, pungent|
| Common Uses | Eating raw, baking, salads | Flavoring, woodworking |
So, while both are walnuts, they have distinct characteristics and uses.