An "Entry Process" is how many PHP scripts, Cron Jobs and SSH commands you have running at a single time. Our shared hosting has the following limits: https://support.stablehost.com/en/articles/2087015-web-hosting-resource-allocation
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 25 limit Entry Process doesn't mean only 25 people can be on your website at once because the likelihood of all 25 people hitting your website at the exact same second would never happen.
We've seen an entry limit of 25 usually handle 30-40 visitors on your website at a time. If you have a low traffic website but are constantly at 25 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 article about CloudLinux and Shared Hosting Limits.