they fork, and create a new coin. then some bitcoin holders claim their new coin and dump it for more bitcoin or even cash. some others keep holding it, and some don't even bother/risk claiming the tokens.
but all this time a bitcoin holder is a bitcoin holder and will remain that. they just increase the amount of bitcoin they are holding.
the same discussions about security, and where to hold bitcoin and how to safely claim the new fork still are valid. bitcoin gold fork seems to have replay protection now. so it is like bitcoin cash.
Thanks for your response , so is the bitcoin electrum wallet safe enough?