Your PrestaShop installation must know all existing countries in order for your customers to clearly indicate where in the world they live.

There are roughly 200 countries in the World, but PrestaShop has 244 registered. This is because some countries include overseas regions are part of the country proper.
For instance, the French departments formerly known as DOM (Guadeloupe, Martinique, Mayotte, Reunion, and French Guiana) nowadays have equals status as the French metropolitan region. Likewise, Alaska and Hawaii are US States proper.
Still, sending a package to Guadeloupe does not mean sending it to France, if only for the shipping fees. Therefore, the list of countries in PrestaShop actually separates the country from the mainland.

Be default, only your own country is enabled. You should enable them one by one, as needed for your customers. If you are unsure which to enable, check your stats to see the countries with most visitors.

At the bottom of the list, the "Country options" section to only display on your front office the countries that your carriers cover. We recommend that you enable this setting, as it prevents customers from having to scroll through all the country names to find their own.

Adding a New Country

Normally, PrestaShop comes with all current countries in the database. But in the case new ones are created, you would need to add a new country.