A toaster converts electrical energy to heat (or thermal) energy.
A toaster is an electrical device used for making toasts. The process involves putting pieces of bread in the slots of a toaster and using electricity to heat them. The heat is provided by coils that heat up due to passage of electricity and we end up with toasted bread or simply, toast.
A toaster is not the only device capable of doing so. The hot water geysers at our homes carry out the same process and convert electrical energy to heat energy and use the heat, thus generated, to heat the water. Electrical cooktops and heaters are also based on same energy conversion (from electrical to heat energy). Note that conversion of energy from one form to another may or may not be a very efficient process and we may observe energy loss in the process.
Hope this helps.