This depends entirely on your home carrier and plan, so the first stop is your carrier's roaming page or app, where you can usually search by destination country and see exactly what applies. Broadly, there are three models in the market: plans with roaming genuinely included in certain regions, carriers that sell daily or weekly roaming passes, and pay-as-you-go rates that are almost always brutal and worth avoiding.
Even when roaming is included, read the limits. Many carriers cap included roaming data below your domestic allowance, throttle speeds abroad, or apply fair use rules that cut you off or start charging after an extended period overseas, since these plans are designed for holidays rather than living abroad.
Before flying, do three things: check the destination against your plan's included list, note any daily fee that triggers the moment your phone connects, and if the terms look bad, disable data roaming and plan on a local SIM or travel eSIM instead.