They work with a similar concept of creating a vacuum but the traditional ones use heat (usually from a candle) to warm up the air inside the cup, causing a negative space and hence a vacuum effect. Or at least that was how it was explained to me anyway.
@be3169 apparently there is wet cupping too, which involves the placement of cuts on the skin prior to the cupping practice, which then draws out blood. I dont know about you, but I’m not sure I fancy that.
When you warm the air it expands.
Once the glass or cup or whatever is placed on the skin the air inside cools and contracts leaving a partial vacuum inside the vessel. This partial vacuum draws in the skin under the vessel.
A vacuum pump will produce a lower pressure inside the cup than the warm air method but is more mechanical and not as sensual.
There we go, I remembered it was something to do with the air and vacuums but evidently I got it a bit muddled lol. Thankyou for the correction.
I do agree that the vacuum pumps aren’t as sensual. Fine if you want a more medical/cyberpunk feel to your sessions I suppose, but not personally for me.
Retired secondary school science teacher 
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Don’t say that @rockstar, I’ll be wanting to move in 
I was a complete science nerd back in my youth, I signed up for after-school science club and everything.
I may or may not have had a periodic table shower curtain as featured in The Big Bang Theory 
All in for cuping hickeys but not so much for the blood sucking thing. Will have to do some research on that one.
I did a bit of reading on it and the risks on it do seem much higher. Apparently it’s more popular outside of the US and I should imagine the same for the UK. I did find a centre in Birmingham which offers wet cupping but their website was full of typing errors and business communication via Whatsapp, which probably tells you all you need to know.
I am going from memory here but I believe the whole cupping thing originated in Asia. Don’t know anything about the wet cupping.
From doing a quick bit of research, cupping apparently originates in the Arabic lands, in ancient Egypt. I do understand though, it does have a traditional Asian medicine feel to it.