Preheat usually uses both bottom burner and top broiler burners, and should (theoretically) reach desired temp sooner than just bake.

And FWIW, pre-heat just gets the air hot, and as soon as you open the oven door, the air temp drops. If you are baking pastries and bread, you want to keep heating the oven before use, ensuring that the walls and surfaces will hold the heat a little better. Or use heating stones. But if you are cooking a casserole, it probably won't make a difference.

Just know that every time you open the door, you loose heat.

Which is why I always preheat my oven to 50 degrees above the temperature I'm going to bake anything at.

I wonder if by preheating the oven at one temperature, would allow you to bake at another?

What does it say about it in the user guide?

Thanks for the responses. I will check if "Preheat" does in fact use both the upper and lower elements, and perhaps I can measure the time it takes to warm-up using each button. The user guide does not make any distinction between the two functions except to say that when using the "Preheat" button the oven switches to "Bake" once the desired temperature is reached. This would perhaps suggest that the upper element is used during "Preheat".
I will investigate and post my findings.

I have measured the time it takes for the oven to warm up to 350. Again the "Preheat" and the "Bake" buttons appear to perform the same. From a room temperature oven to 350 degrees, both settings took about ten and a half minutes.
In each setting, both the upper and lower elements are used, with the lower (hidden) element doing most of the heating. Periodically, throughout the process the lower element will cycle off and the upper element will come on.
The upper element never stays on long enough to become red, but you can tell from the panel display which element is in play.
So the setup remains inexplicably curious.

It sounds like a gimmick to me.

One thing I learned on this forum about pre-heating, is that just because the bell rings on your oven, doesn't mean that it's reached the desired temperature. Someone pointed out that when their oven beeped to tell her it had reached, say 350 degrees as an example, the thermometer she had placed in the oven only read 275. I don't remember the exact numbers, but the difference was significant. I tested my oven, and it was the same - although it was supposed to be 350, it had only reached about 275. So, use an independent thermometer if the starting temperature is important.

Sally

Good advice, Sally. Thanks, one and all.

Its really a funny thing but I never preheated an oven in all the time I've been baking which is maybe 45 years or so! The only thing I noticed was that whatever I was baking just took a few minutes longer to reach doneness! I've baked pies and cakes and casseroles and breads and never saw much of any difference. My daughter came to visit a few years ago and chided me about it so now I do preheat. The only exception was when I baked cookies and then I did preheat.
Joann

On my old double oven unit, the top one didn't have a "preheat" option. You set the temp and the one element came on to heat up. The large bottom oven had bake and preheat. As mentioned before, preheat used the broiler element to help heat it up much more quickly.

My new unit (single oven) has no option for just "bake" when you turn it on. Push the button and set the temp, then the "Pre" (preheat) display comes on until supposedly up to temp then clicks to the temp. I can't tell if the top element is on, and I suspect if it is, it's on low. I'll have to take a look. I kind of miss the old unit in this respect, but not in the cooktop.