Since it automatically sets it for me in my .env file when I create the app, I'm not sure when I should run it.
In addition to that, if a second developer comes in, and clones the app, does he/she need to run php artisan key:generate ?
How do we know exactly when to run php artisan key:generate ?
php artisan key:generate is a command that sets the APP_KEY value in your .env file. By default, this command is run following a composer create-project laravel/laravel command. If you use a version control system like git to manage your project for development, calling git push ... will push a copy of your Laravel project to wherever it is going, but will not include your .env file. Therefore, if someone clones your project using git clone ... they will have to manually enter php artisan key:generate for their app to function correctly.
So, TL:DR the only time you need to call php artisan key:generate is following a clone of a pre-created Laravel project.
Side note: If you try to run a Laravel project with your APP_KEY set to SomeRandomString (which is the default in your .env.example file, you will actually get an error:
No supported encrypter found. The cipher and / or key length are invalid.
