Your eSIM will be delivered to the email address you provider when you purchase. Some providers require you to create an account before you can purchase their eSIM products, so in that scenario your eSIM might wait for you in your user account after you have purchased it. You'll usually receive installation instructions for your eSIM
If you are not sure about what exactly you will receive, here is an example of what you receive when you buy an eSIM on Airalo.com.