I don't think this is about steam, it's about the vapors. I benefitted from inhaling the vapor smell with the pad that came with the item.
No, you can't use boiling water. No, it is not electric.

But to me, it is like using the vapo rub in a much easier manner. No mess, and just as effective.

If I want steam, I'd get one that you plug in. But if I want vicks vapo rub vapors, I would use this.

And I do! And it does the job!

This review wouldn't be so negative if this product wasn't sold to me using the word steam. I had intended to get a product like the Vicks Personal Steam Inhaler - but ran across this product for less money - and as far as I could tell from the write up - this product did the same thing.
No.
You simply put hot tap water in what is basically a plastic mug without a handle. Oh you get this useless facemask with it. Where's the steam? In case you were interested in providing your own steam - it is clearly marked all over that it is unsafe to use boiling water.

Save your money. Use a mug of steaming hot water with a vicks vapo-thingy of your choice in the water. That's what I ended up doing.

It's criminal that they are allowed to use the word steam.

Do not buy this - get an electric one. This is simply a cup and a plastic funnel that you put hot water in.

This was not what I was expecting. You pour hot water, not boiling, in the base and add the disc to inhale the fumes. I used mine with essential oils and I get better results over a sink full of water. Does not produce steam like I would like. Easy to use, made for all parts to come apart. Easy to clean.

After reading the reviews here I wondered why on earth I had purchased this contraption. But I decided to give it a try because I had a VERY stuffy nose, it was late at night, and I was desperate. When I breathed in the vapors as indicated by the illustration on the directions not much happened. Then I tried placing my face/mouth directly on the unit creating a "seal" and breathing in deeply. The medicated vapors flooded my throat and lungs and then to my surprise I was instantly able to breathe freely through my nose! After six days of dealing with an incredibly stuffy nose, this seemed like a miracle to me! The relief was temporary but could be attained again by repeating the process. It really did help to open my nose, cool my throat, and quiet my cough. This will be coming along with me on vacation next week!