Toast is bread that has been browned by heating. The browning is the result of a Maillard reaction, altering the flavor of the bread and making it firmer so that it is easier to spread toppings on it. Toasting is a common method of making stale bread more palatable.

Toast is commonly eaten with butter or margarine, soup or sweet toppings, such as jam or jelly. Toast is a common breakfast food.

The word toast comes from the Latin 'torrere' 'to burn'. In the 1400s and 1500s, toast was discarded or eaten after it was used as a flavoring for drinks. In the 1600s, toast was still thought of as something to be put into drinks.

In a modern home kitchen, toast is usually made in a special-purpose electrical appliance, a toaster. Sliced bread is placed into the slots on the top of the toaster, the desired level of toastiness is set, and a lever is pushed down. The toaster pops up the toast when it is ready. Many brands of ready sliced bread are available, some of which specifically market their suitability for toasting.

Toasted bread slices may contain Benzopyrene and high levels of acrylamide, a carcinogen generated during the browning process.

More Info: en.wikipedia.org