"Cron" is a process that is run every hour by the web server. You're probably interested in it because it controls when the newsletter is sent.
Point your mouse at the small icon in the admin menu, in the very top left corner of the page. The admin menu drops down. Click on "Run cron."

Cron will give you an update once it's run. The newsletter emails should be sent.
Note: It is not necessary to run cron manually. Cron runs once an hour, 24/7.
On a web server, you don't want independent programs running all the time because they'll slow down the server. But you still want certain processes to run on a regular basis (such as checking for software updates).
Cron is a small process that runs continually on the server, and it in turn runs other programs on a periodic basis. It has a list of which programs it will run, and how often.
The Consortium web site is run on a "content management system" called Drupal. Drupal has its own code that it uses for periodic tasks like checking for updates and sending newsletters. When you click on the menu item "run cron," you're really running Drupal's cron code. This is the code that cron will run every hour; you're just running it early.
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