Who is for install.php during Mediawiki install?

I’m installing Mediawiki 1.31 on CentOS 7. I’m following the instructions at Manual:Installing_MediaWiki. I’m having a trouble running install.php.

An earlier step had me create the MySQL database using:

CREATE DATABASE wikidb; CREATE USER 'wikiuser'@'localhost' IDENTIFIED BY 'password'; GRANT ALL PRIVILEGES ON wikidb.* TO 'wikiuser'@'localhost' WITH GRANT OPTION; 

Next, I am suppose to run php maintenance/install.php. However, they omit instructions on how to do so. The script is failing with:

# php maintenance/install.php Argument <admin> required!  CLI-based MediaWiki installation and configuration. Default options are indicated in parentheses. ...  Arguments:     [name]: The name of the wiki (MediaWiki)     <admin>: The username of the wiki administrator. 

My question is, who is <admin>? Is it root on this machine? Is it wikiuser from the previous step? Or do I need to create another user and give it root privileges for the database? Or something else?