If you have an HTML website, it likely uses a small amount of system resources as it's static, but this is not the case with dynamic database-driven websites that use PHP scripts and provide considerably more capabilities. This sort of sites generate load on the hosting server every time anyone browses them, as the server needs time to execute the script, to access the database and then to deliver the data requested by the visitor's Internet browser. A popular discussion board, as an illustration, stores all usernames and posts inside a database, so some load is created every time a thread is opened or an end user looks for a given phrase. If lots of people access the forum simultaneously, or if each search involves checking tens of thousands of database entries, this could generate high load and affect the performance of the site. In this regard, CPU and MySQL load data can provide info about the site’s performance, as you can compare the numbers with your traffic stats and see if the site must be optimized or migrated to another kind of hosting platform that'll be able to bear the high system load if the website is very popular.
