An entry process is the number of PHP scripts running at the same time in a website. It can have a limit as 20 PHP scripts at a time. This means not that only 20 visitors can visit a web page at a time. It means that entry limit of 20 usually handles 80-100 visitors at a time on the same process or the script. Cron jobs, shell scripts, and other commands also use one entry process for the duration of time they are running. When the limited number of process is being used and if another user tries to visit the website, then the visitor will get a 508 error. This will not just slow down the speed of the website, but it limits the user service.