Toaster oven is a home appliance which is not common in Europe. Then, it is much popular than pop-up toaster which is also available in Japan.
I assume toaster oven is better due to you can bake not only toast but also gratin and pizza. Then, it is better to use toaster oven than microwave oven to reheat deep fried foods with breadcrumbs.
The way to use the appliance is very simple. Open the door, place the toast bread or gratin on the rack and close the door. Choose the temperature and the timer. Toast are 250 degrees Celsius for 2.5-3.5 minutes(if you use above toaster oven). Pizza is 220 degrees Celsius for 6-7 minutes.