Each shared hosting plan lists four limits. CloudLinux applies them to your account alone, so another customer on the same server cannot take your share, and your site cannot slow theirs down.

• CPU: how much processor time your account can use at once. 100% is one full core.
• RAM: the memory that all your account's processes can hold together.
• Disk I/O: how fast your account can read and write files, in MB per second.
• Entry processes: how many requests, mostly PHP pages, can run at the same moment.

Entry processes are the one that surprises people. With 20, twenty visitors can be waiting for a PHP page at the same time; the next one may get an error or wait. Page caching helps a lot, because a cached page never reaches PHP: on WordPress, turn on the LiteSpeed Cache plugin.

In cPanel, Resource Usage shows how close your account comes to each limit. If it often reaches one, it is time for a bigger plan or a VPS.