When a visitor visits a website, a request is raised on the server. This request is handled by a process. The process creates the webpage, gathers its necessary resources and sends the webpage as response to the visitor.
In many plans, there is a cap on the number of processes that can be started per account. This factor determines the number of simultaneous connections possible. For example, suppose the number of processes is 10 and each process can handle one request. In this case, you can have only 10 simultaneous connections to your website; any additional request will be queued and serviced only when pending requests have been completed. This has adverse effect on the experience of visitor.