An entry process, directly translated means a 'process which enters LVE', or, a process which enters / runs inside your LVE container / account.
Entry processes, as a combined term, equates to the processes which run within the LVE / user account simultaneously.
Your 'Entry Process' limit essentially means that you can run that quantity of simultaneous processes within the account at any given time. Whats important to point out however, is that an Entry Process can take a fraction of a second to complete (or the opposite, where a process hangs for some time).
By example, think of a PHP script, which typically take a split second to complete or process. From that point onwards, the process dies, and your 'available' LVE allocation for Entry Processes increases with an additional spare slot. However, if you have a process which runs for a longer period (such as, a longer running PHP process or script, or a cron which takes some time to complete), it will continue to use that Entry Process slot.
As such, its a common misconception that 'Entry Processes' equates to the number of simultaneous visitors, however this isn't the case. The reason for this, as explained above is that a single process may run for a split second, which means you can essentially run more than the EP value as simultaneous visitors (assuming that the Entry Process dies, and the page loads in a reasonable time).
If your account exceeds its LVE limits for 'Entry Processes', those additional resources which run 'above' the limit count, will be killed by a kernel process called 'SIGKILL'. The result of this, is a 503 'resource limit reached' error.
Our hosting plans come with varying levels of Entry Processes (albeit, slightly higher than many providers). If you are hitting your EP limits, it may be worth checking the 'Resource Usage' section of your control panel or reach out to our support team for assistance.