WordPress and many of its plugins need to wake up and do some work for example to shedule posts, maintenance, refresh caching and so on.
Normally it does this while a visitor or searchengine requests a page and this slows down this user or searchengine which leads to suboptimal expirience or downgrades on the ranking.
So many people disable this behavior and run a linux sheduler (cronjob) to call the wp-cron.php file by themself over HTTP. Continue reading