Your account displays the amount of each resource it's using, as well as its maximum.
For definitions of these resources, see How do each of cPanel's resources affect my site?
Your account's current resource usage displays on the left.
To see if you have hit the limit for your account's CPU or entry processes/concurrent connections, click CPU and Concurrent Connection Usage. If you see "Your site has been limited within the past 24 hours," it means your site has consumed all of its available resources in the last 24 hours and to prevent degraded performance on your website, you should consider upgrading your account's resources.