Ok.... What is a Geyser? Is that like some French thing that squirts water up your ass? My stove is gas too....
No, that's a "bidet".
"Geyser" it's a common term for a water heater in the UK. The name came into the language from a product name, much as "Aspirin", "Styrofoam", "Velcro", "Band-Aid", "Sharpie", "Escalator", etc (among hundreds of others - a quick search turned up this list of generically-used trademarks).
To expand on this a bit: The average person with a US-centric world view probably only knows of tank-type water heaters, which are far less common outside the US. In Europe, where people still live in houses that predated indoor plumbing or at least predated hot water from a tap, they may heat water anywhere from a centralized on-demand instant heater through a point-of-use on-demand water heater. Large tank water heaters would be impractical to install in any house that was not initially designed for one. As a result, they're also harder to come by, so newer houses are also designed around on-demand water heaters...
For a more humorous example of English-American language incompatibility, see "Trousers", which Americans call "Pants".