A travel eSIM is a data plan you download, not a plastic card you hunt for after baggage claim.
The phone has to be able to take one
The handset needs eSIM hardware, and it needs to be unlocked. A phone still on a carrier lock often refuses a second profile even when the settings menu shows an "add eSIM" row. iPhones from the last several generations support it. Many Androids do, and the menu names differ: Network and internet, SIM manager, Mobile network. If you cannot find the row, search the exact model before you pay for a plan. Airalo keeps a compatibility list inside the app. Use that, not a forum from 2022.
One physical SIM plus one eSIM is the useful setup. You keep your home number for calls, banks, and WhatsApp. The eSIM is data. How to stop the home number from roaming is in keeping your number abroad.
Read the validity line before you install
Airalo's own help says most plans start when the eSIM joins a supported network in the destination. Installing in your kitchen does not burn day one. Some plans start at installation, even if you are still at home. That difference is on the package details, and Airalo explains it here. Open that line. If it says the clock starts on install, do not install a 7-day plan a week early.
iPhone, then Android
On an iPhone the path is Settings, Mobile Service, Add eSIM. Scan the code or enter the details by hand. Label the line "Trip" so you do not toggle the wrong one at midnight. Set the default voice line to your home number. Set mobile data to the trip line.
On Android, direct install from the Airalo app works on some models. Otherwise use the QR or the SM-DP+ address and activation code from the app. If data will not flow after you land, the missing piece is often the APN, which the app lists under the plan. Turn data roaming on for the eSIM. Turn it off for the home SIM. That second toggle is the whole bill.
What an eSIM will not do
Most Airalo plans, including the regional ones, are data only. They do not give you a local phone number for calls and texts. WhatsApp, iMessage, maps, and mail use the data. A bank that insists on an SMS to your home number still uses the home SIM, which is why you leave that line installed and merely stop it from using data.
A France plan works in France. It does not quietly cover the train into Switzerland unless the plan's country list says so. Multi-country trips want a region plan, which is the subject of one eSIM for a Europe trip.
Can I install at the airport?
Yes, if the wifi holds still long enough to download the profile. It often does not. Home wifi the night before is the reliable version.