An eSIM is a SIM card built right into your phone. There is no tiny plastic chip to pop out and no shop counter to visit. Instead, you buy a data plan online and your phone downloads it.
Think of it like adding a second phone line that only does internet. Your normal home number keeps working for texts and calls. The eSIM quietly handles your data while you are in Bermuda.
Because it is all digital, you can set the whole thing up at home before you fly. When you land at L.F. Wade International Airport in St George's, you are already online.