Principle of operation
A toaster oven generates heat through an internal heating element (usually an electrical resistance wire) and uses the high temperature to toast the bread slices to the desired level. Generally, toaster ovens have adjustable baking levels, which control the heating time and temperature to meet different user preferences for the degree of bread slices baking, ranging from light golden brown to dark brown.
Structural features
Slots: Used for bread slices, usually 2 - 4 slots, the width and length of the slots are designed according to the size of common bread slices to ensure that the bread slices can be heated evenly.
Control buttons or knobs: These include the power switch, toasting level adjustment buttons or knobs, and so on. Some high-end toaster ovens may also have buttons for other functions such as cancel function, reheat function, defrost function, etc.
Heating element: hidden on the sides or top of the toasting slot, generates heat when energized and transfers heat to the bread slices.
Crumb Tray: Located at the bottom of the toaster oven, it is used to collect the crumbs that fall off during the toasting process for easy cleanup and to keep the oven clean.

A toaster oven generates heat through an internal heating element (usually an electrical resistance wire) and uses the high temperature to toast the bread slices to the desired level.