Localization is the feature that allows you to specify the language that's different from a default one (English)
Changes will be applied only to the user-mode - the surface that the end-users of your app will be interacting with. The builder mode will remain in the English

Setting up the language

Step 1: Check if your language is on the list

Inside the app builder, go to the top left corner and click on your account logo:
Then scroll down to the bottom of the page and find the Language dropdown. Choose your language from the dropdown:
If your language is not on the list, reach out to our support (bottom left corner in the app) with the request of adding your language

Step 2: Pick your language and save the changes

Once you save the changes, all the users who sign-up/log-in into the app (in the user mode) will see the localized version