@mayintoronto Pies must initially contain a liquid filling within a crust, so a taco cannot be a pie because the filling would drip out.
- The filling is permitted to set after cooking, for example a cheesecake or a quiche
- The pie may optionally be covered with crust or remain open. A shepherd's pie is technically a layered open pie because the potato topping is not the same as the lower crust.
Glad I could clear that up for you!