If you log into cPanel, you will see on the right hand side "Entry Processes" with a number.
An "Entry Process" is how many PHP scripts you have running at a single time. Our shared hosting has a limit of 20 PHP scripts at a single time.
Keep in mind an "Entry Process" only takes roughly a fraction of a second to complete, therefore most people get it confused with how many visitors they can have on their website. A 20 limit Entry Process doesn't mean only 20 visitors can be on your website at once because the likelihood of all 20 people hitting your website at the exact same second would never happen.
We've seen an entry limit of 20 usually handle 60-100 visitors on your website at a time. If you have a low traffic website but are constantly at 20 Entry Processes, it means something is wrong with your scripts and they are hanging around longer then they should.
If you want to read more about this, please check this page: CloudLinux / Shared Hosting Limits Explained