The Site information screen can be reached at Configuration | System | Site Information (admin/config/system/site-information).

It allows you to set some important site-wide parameters for your site.

Cron is a technical term referring to timed processes that run on a webserver.

Typically, these are used for background tasks like cleaning old stale cache data and indexing search terms. Many Drupal modules will react to a cron event and perform relevant background tasks.

Depending on the purpose of your site, it may be appropriate to run cron once a day or once a minute. This choice really depends on what background tasks will run and how often they need to be triggered.

You can either run cron manually or set how often it should run automatically. The default value is every 3 hours and this is an appropriate setting if you are not sure.

The latter is a useful setting to have switched on locally when you are developing a website as it will essentially simulate a cron run every three hours. However, it may become annoying to experience the delay cron running every time you go back and visit your site after anything more than a three-hour period away so you may choose to switch it to Never and only run cron manually when you need to test its effect.

For a live site you will need to configure your web server to call the cron task in Drupal periodically, and the setup will vary depending on where you eventually host your site. The setup is, therefore, beyond the scope of this module but is detailed thoroughly at: https://www.drupal.org/cron

Also note that there is a link in this screen that allows you to run cron manually from outside of the site. It's deliberately a rather long URL so that people cannot guess the path.

To manually simulate a cron run simply from this screen, click on the Run cron button.