The nature of the shared hosting environment is to offer a single server to a number of clients at the same time. Those clients are sharing the resources of the server for their websites. However, to keep the service stable and secured, limitations are set for each account on the server. This ensures the equally divided resources on the server and the smooth performance of all services.
One of the services we use to bring up a high level of security and performance is CloudLinux. It is an OS, which sets limits on each account on the server and provides real-time monitoring for better management of our shared hosting infrastructure. When CloudLinux is installed on the server, each account has it’s own “LVE”. (Lightweight Virtual Environment)
Each LVE (cPanel user) is then assigned a limit to the amount of CPU they can consume, the amount of memory they can reach, and the number of “entry processes” (essentially concurrent number of processes) that they can have, etc.
If any of those limits are reached by the LVE, you will experience performance issues or notices to inform you about the amount of resources used on your account. You can always monitor your resource account activity via cPanel -> “Resource Usage” icon from the “Logs” section. When you access the menu you should be able to see different tables with information for the resource usage in the last 24 hours or another period of your choice.