It is not mentioned in the docs and in the CLI help, it says - Creates the Migration Repository.
What does that mean?
When I run thus command it says - database laravel not found.
Laravel creates a migrations table in your database to keep track of what migrations have already been ran on your database. If you run php artisan migrate:install, this table is created.
This table makes sure that when you run php artisan migrate, migrations that have already been ran on the database are not done again.
When migrating, this table is also created automatically, there is no need to run the install command beforehand.
The reason for your error is probably because you have not set the correct database credentials in either your .env file or config/database.php file.