The benefit of a speed oven is that it combines the speed of a microwave with the roasting effects of a convection oven. So your food cooks microwave-fast but gains a traditional “roasted” finish.
A conventional convection oven heats with electricity or gas and uses a fan to circulate the hot air. A speed oven uses convection heating and fans but adds microwave heating, which can vastly shorten cooking times. Some also have a grill element.
Many speed ovens have the option to only use the elements you want - only the microwave, for example, or only the convection oven - so they can be used in a “regular” mode.
Anything that can be roasted in a regular oven can be cooked in a speed oven. And any job a microwave can do - like thawing frozen food – a speed oven can do as well. And if your speed oven has a grill element, you can also broil.
Speed ovens are made by major manufacturers like Wolf, Miele and Bosch. You can see these and more at Coast Appliances.